We only got help from them during ours because they hated Britain. We were already in debt it just pushed us deeper. Their revolution didn't end up too well in the end and I doubt we could have changed that. The large amount of money we gave Napoleon did give them some assistance however.
Currently, English seems to be the dominant language. I have talked to a Japanese student that says that English is a required course in Japan. I feel that this trend will only grow in the future.
None singlehandedly. WWI we just came in the end and didn't really do much. WWII our push was good, but our soldiers were very young and unexperienced, our help was purely moral. Therefore, it's debatable how much we "won" that war for them.
and that's really the only wars we've joined after they have.
Even if we had won WWII for them, it doesn't exclude the fact that we were off-focus after 9/11 and they couldn't get behind it.