I'm hardly one to answer this being Canadian, but while the Americans did fight for largely noble causes (no taxation without representation, the establishment of a constitutional democracy [or Republic for the purists]), the main reason for their starting the war was entirely lacking gratitude.
The British King fought off the French in order to prevent the colonies from being taken over by France (I believe that's why he fought them anyway) and because the war bankrupted the treasury he logically assumed that the colonists wouldn't mind paying something for that protection.
It started the typical American response we've seen so often since: opposing virtual any and all taxes no matter how justifiable they are or beneficial they may be.
First of all, its not like this was some sort of magnanimous gesture on Britain's part. The French and Indian War, like every other war fought during the colonial era, was one of territorial conquest. I doubt the British government cared very much about the colonists themselves; their main concern was over who was ruling them.
Second, it's not like the colonists were sitting around twiddling their thumbs while Britain did all the fighting. Numerous colonists (George Washington, Robert Rodgers, and John Parker to name a few) fought against the French, and Britain probably couldn't have won the war without them.
Third,
so-called gratitude has nothing to do with political rights. As TNF said earlier, the size/need for the taxes was not what was being protested. The colonists had been paying taxes to their local governments for years and never batted an eyelash. The issue was that
the British government voted to take their money without giving them a single vote on the matter. If you would rather live in a country where government has absolutely no reason to listen to you, then by all means oppose the American Revolution. To assume, however, that the colonists were somehow obligated to surrender their right to self-government because they benefited from one of Britain's many wars of conquest is, frankly, ridiculous.