Why did many colonies favor declaring independence?
Because all were affected in varying degrees by negative British laws.
While under English rule, most Americans considered themselves equal in stature to their brethren in England. But when in the 1760s England made laws specifically tailored towards America, most of which were considered "coercive" by the colonists.
The colonies may have liked their independence via their being corporate entities as chartered by England, but none liked the idea that the freedoms they had guaranteed them under those charters were being eroded, and at an ever increasing rate.
Regardless of the colony a person came from, he also called himself an American and that was what bound them together in the end.