What do you call a group of people that create laws (this is in regard to the American Revolution)?
There was not any particular special word for a group of people that create laws that was used during the Revolutionary War. There are a few different words that might be the answer to your question.
Generally, a group of people that create laws is called a legislature. That is a generic term for lawmakers. In the colonies at the time of the Revolution, the term used for legislatures in many of the colonies was "Assembly." Colonies had assemblies that made laws. The legislature for the British Empire as a whole was called Parliament.
So, one of those three ought to be the answer you're looking for.