France and the USA were technically allies during the War of 1812 against the British, and yet, there doesn't seem to be any interaction when I read about the war. Given the fact that the USA was in desperate need of help, getting some French aid like during the American Revolution would have been useful.
They weren't technically allies but co-belligerents, meaning they were both fighting separate wars against Britain. France had fought longer and harder against Britain than anyone, ever. They were also engaged in a little thing called the French invasion of Russia in 1812(not to mention the ultimately 7 year long Peninsular war). Russia was of course a pawn of the British at this time, so France was giving immense indirect aid to the Americans by waging almost continuous war against the islanders since 1792. And if you wish, since 1689.
It was Britain's heavy handedness with everyone during it's wars with France, especially the American merchantmen, which led to the war of 1812.