The French and Indian war began in the Ohio River Valley as a conflict over who the land belonged to. The French claimed the Ohio Valley as did the states of Virginia and Pennsylvania. The American colonies wanted land more than anything else where they could own their own farms and be independent.

The American Colonies fought the French and Indians to gain control of the lands west of the Appalachian mountains. The first battle of the French and Indian war was fought between Virginia militia lead by George Washington and the French over control of the three rivers area of what is now Pittsburgh.

At the end of the French and Indian Wars the American Colonies felt that they had earned the right to settle in the Ohio River Valley.
The British having won control of Canada and the profitable fur trade wanted to keep the Indians, that had sided with the French, happy. To achieve peace with the Indian tribes and maintain the fur trade that depended on the Indians passed a law in 1763 that prohibited settlement west of Appalachian Mountains.

The American Colonies felt betrayed and cheated by the law that blocked their settlement of the west. The bitterness and resentment that the prohibition of 1763 was a major cause of the American Revolution.

Consider this from Jeffersons letter to Madison on December 20, 1787:

"...I will now add what I do not like. First the omission of a bill of rights providing clearly & without the aid
of sophisms for freedom of religion, freedom of the press, protection against standing armies, restriction
against monopolies, the eternal & unremitting force of the habeas corpus laws, and trials by jury… a bill
of rights is what the people are entitled to against every government on earth, general or particular, &
what no just government should refuse, or rest on inferences."

https://www.tomrichey.net/uploads/3/2/1/0/32100773/thomas_jefferson_to_james_madison_-_20_december_1787.pdf

(Original version: https://www.loc.gov/item/mtjbib003193/)

Basically, the US was fully isolationist pretty much up until Pearl Harbor. However, FDR wanted to help the Allies in Great Britain, so the neutrality acts that were passed created loopholes that allowed him to send aid to Britain without fighting the war. The Neutrality Acts of 1935 and 1937 banned selling arms to belligerent nations (to avoid taking sides), but Britain and France hadn't gone to war yet, so FDR could still send aid to them.

In 1939, the US realized it needed to send more help, so it came up with a new Neutrality Act of 1939. This one said that belligerent nations could buy guns, but they had to pay in cash and use their own ships (to avoid naval conflict such as the Lusitania incident prior to WWI). This was called the Cash-and-Carry Policy.

After France was taken and Britain ran out of money, the US passed the Lend-Lease Act which said that the US could lend support to Britain in the form of arms or other aid without immediate payment (it wasn't really lending, since they weren't going to get any of the items back, nor were they going to get paid back).

Through all of this, the US still declared neutrality to avoid warfare, but the Axis Powers were actually fully aware of the US's unofficial alliance to Britain.

They didn't declare war simply because they didn't want to fight the US yet (divide and conquer, essentially. We were also the biggest potential threat to the Axis Powers).

Source: AP US History

The Free Soil Party was created in 1848. The main purpose of this party was to oppose the expansion of slavery westward. A lot of the Party's support came from 2 groups. A groups of Democrats called "Barnburner Democrats" and "Conscience Whigs." Barnburner Democrats were an anti-slavery faction within the Democratic party that was mainly based in New York. The Conscience Whigs was a faction in the Whig party that included many Northern Whigs who also opposed slavery. Historians agree that the Free Soil Party was founded on the basis of limiting/eliminating slavery.

In the Presidential election of 1848, they nominated former Democratic president Martin Van Buren. Buren, who was a Barnburner Democrat, chose Charles Adams, a diplomat and politician who is also the son of John Quincy Adams. In the election, they didn't carry any states or receive any electoral votes. They did get a little over a quarter of a million votes, or about 10% of the popular vote. Compare that to the winner of the election, Zachary Taylor of the Whig Party, who got 47% of the popular vote. Buren was a smart politician and he knew that the Free Soiler's had almost no chance of winning the presidency. So he ran so that he would split the Democratic vote and thus give the presidency to the Whigs. The reason is Buren (a former Democratic president) didn't like the Democratic nominee Lewis Cass and he was disappointed in where the party was headed.

In the Election of 1852, the Free Soil Party did not have as big of an impact or voice than in the 1848 election. They were still the largest 3rd party, but the Compromise of 1850 had a lot of Barnburner Democrats supporting it. In which they returned to the Democratic Party, which depleted the Free Soil Party's base. Also a lot of the Conscience Whigs went back to the Whig party as well. At the party convention, they nominated John Hale, a senator from New Hampshire, as their presidential candidate. They nominated George Washington Julian of Indiana as the Vice Presidential nominee. In that election they received 4.9% of the vote.

The Kansas-Nebraska Act of 1854 brought back the anti-slavery movement. The Free Soil Party was largely absorbed by the Republican Party. The Free Soil Party was officially dissolved in 1854.

Company towns, towns where virtually all property and services were controlled by the company that owned the town, started appearing in America shortly before the Civil War, They were characterized by a paternalistic attitude towards the workers by the companies' owners. In hard times, a steady wage and company-provided food and shelter can sound like a pretty good deal, but the wages were often paid in "scrip," company-printed currency that could only be spent at stores and establishments owned by the company.

The effect was to increase workers' dependancy on their employers. These employers dictated what the workers could do when off-duty, what churches they had to attend, who they would vote for. The dependancy relationship invited comparisons to slavery. Chattel slaves, the kind the South was infamous for, were kind of expensive to buy and actually represented a bigger investment than "wage slaves."

Employers defended the practice as a moral imperative, calling it "Capitalism with a conscience." It kept otherwise unemployable people fed, sheltered and in church; what other justification was needed?

Many company towns operated in western Pennsylvania and West Virginia, coal country. The most famous, Pullman, was outside of Chicago and the site of a major strike in the late 1890s. The explicit practice died out in the 1920s, though some mining towns had elements of wage slavery well into the 1960s. Company towns have been represented in books ( The Grapes of Wrath ), film (Matewan ) and song ("Sixteen Tons" by Tennessee Ernie Ford, quoted on the title).

After the Civil War there was a difficult situation in the former Confederate Nations.
Apart for, well, losing the war and losing the best of their adult generation killed or maimed on the battlefield the economy of the South was destroyed (because of the blockade and the lack of hands for the agriculture) together with the most important cities of the South (Atlanta, for example).

Towards the end of the war in particular General Sherman decided to organize an incursion or "march" towards the sea (cutting in half the Confederate forces) in which allegedly the soldiers were encouraged to make a "scorched earth" action.
According to some authors (Farid Ameur) this was probably the worst and fierce "punitive" action of this dimension ever performed in the US.

So where the Ku Klux Klan comes into this?
The KKK was born from the resentment and "outrage" after the tragic end of the war to oppose the new rights of African-American and to try to interfere with the decisions of the new governments (considered as puppets of the North) and making them ineffective in changing the society to become a more tolerant one.

The KKK operated as a secret terroristic organization trying to intimidate opposers and carrying out violent actions against African-American or politicians considered enemies of the South.

Interestingly there are two movies depicting the situation after the war:
1) The Birth of a Nation (1915): this is a kind of weird movie where the KKK is depicted as defender of the oppressed white southerners (the strange thing is that African-American in the movie are actually White People with make-up...!).
2) Gone with the Wind (1939): where you can see the fire of Atlanta and the devastation produced by Sherman March (although if I remember correctly there is only a slight description of a KKK like action of sabotage).