Related to that, how about the Battle of the Plains of Abraham? While it was larger, if the French had won it, the history of the next 25 years or so of North America might have been quite different. Would the US colonies have revolted with a major French presence still on the continent? Or would the French support the revolt, leading to a quicker American victory, with even greater ties between the US and France (not to mention whatever might replace Canada in this alternative)?
The battle involved fewer than 10,000 troops in total, but proved to be a deciding moment in the conflict between France and Britain over the fate of New France, influencing the later creation of Canada.[4]