Question

When did the United States become involved in World War I? Why?

Answer 1

The USA entered war in 1917, official reasons are contested.

Explanation:

The sinking of the Lusitania by German submarines in 1915 is often pointed out(since around 132 of its passengers were American) as the reason why Woodrow Wilson had the USA enter war on April, 2nd 1917.

Revisionists claim that it was motivated by financial interests(embodied by JP Morgan, the Federal Reserve) which longed to submit Europe financially speaking. Industrialists were also keen to find new outlets for their production in the war economy(Randolph Bourne famously said "war is the health of the state"). Murray Rothbard is one of them.