Why didn't Americans come and save us from the devil?

They got just sacked by their old masters (https://en.wikipedia.org/wiki/War_of_1812)

The USA wasn't a superpower during the Napoleonic wars. Its rise and its geographical expansion (starting with the Louisiana Purchase) happened a little later.

Also, even if it had been a major player on the world stage (and I'm not suggesting it was geopolitically insignificant), it was arguably even less inclined to get involved with the European powers than it was in 1914. Very isolationist. It kind of wanted other countries to leave it -- and the continent of north America -- alone, hence the Monroe Doctrine.

The United states was busy trying to expand, and take over North America. They were not yet a country that could spare resources, and affect wars over in Europe. They probably would've sided with France anyway, since France was their biggest ally during the revolution.

The US would have been on Napoleon's side if anything.

You do realize that in the early 1800's, the U.S. only had about 6 million people to France's 30 million, right? We were still a brand new country with an almost completely agrarian economy. The industry and massive population growth came much later.

We also fought France's enemy, Great Britain, in 1812, in a war that was fairly inconclusive and basically ended with pretty much a return to the status quo ante -- and even at that we had to suffer the humiliation of having our capitol burned down.

US had it's own problems at the time.

Too busy teaching the British their place.