It really depends on what you mean by largest. Do you mean the most troops involved? The most casualties? The most historical significance? What you must remember is that warfare in North America at this time was relatively limited in terms of armies deployed and casualties suffered. In fact, you were more likely to die of disease serving in the British or Continental armies than you were to die as a result of battlefield action.

That being said, the largest battle in the 1770s was most likely the Battle of Long Island in 1776 between the newly independent American colonies and the British. Even here, however, there were only roughly 40,000 soldiers present, and even less actually saw combat.