Less than half.
I once read that 10% of the population were active participants in the American Revolution.
It might have been the book 1776 by David McCoughlan, an interesting read.
Right you are. Most sat on the sidelines, and many were loyalists. (British sympathizers)
" ... Loyalists were numerous and included small farmers as well as large landowners, royal officeholders, and members of the professions; they were to be found in varying strength in every colony. A large part of the population was more or less neutral, swaying to this side or that or else remaining inert in the struggle, which was to some extent a civil war. So it was to remain to the end ...
From here