While at first glance it seems implausible, it seems to me that the US actually came remarkably close to fighting alongside Britain against France. Thomas Jefferson said that if France retained New Orleans, "we must marry ourselves to the British fleet & nation". I also recall that France seized US merchants trading with Britain. In fact, it seems to me that only pro-French sentiment in the US prevented a Franco-American War. So, could the US have been pushed into actually going to war with France? And what would be the consequences?
I can see two factors that might have tipped the scales. First would be John Adams winning the election of 1800. IIRC, he was more of an Anglophile than Jefferson. Perhaps Adams avoids a breach with Hamilton? A second factor would be a French refusal to sell New Orleans. I don't see it as implausible that Napoleon might refuse (or demand a price that the US couldn't pay). If that happened, surely someone would suggest taking New Orleans (and the Louisiana Territory) by force. The US couldn't face France alone, but if they allied with Britain, that would be a different story.
Obviously, the first thing that happens is that the US attacks New Orleans. I don't know how well defended it was, but eventually the Americans would win. Something like the Lewis and Clark expedition might happen, but with a more military bent, the aim being to secure the territory for America. The US might go after other French possessions in the New World. After or instead of this, the President (be it Adams or Jefferson) would probably send the US Navy across the Atlantic to fight alongside the British. This wouldn't have a major impact (the British already had a decisive naval advantage), but it would give the fledgling US navy some experience as well as letting them learn from the Royal Navy. Certainly the Royal Navy would come to appreciate the power of the American super-frigates. And if the US is allied with Britain, then there would probably not be any widespread impressment of American sailors. However, I honestly don't see the US sending much in the way of ground forces to Europe. Between all of this, we can safely say that the War of 1812 would be averted.
I can see a few long-term consequences. There's a minor possibility that the US takes one or more French colonies in the Caribbean. This might give the US a taste for colonial expansion. The US would also probably retain stronger ties to Britain, but probably not enough to have a major impact. The biggest change would be that without the defeats inflicted upon the US during the War of 1812, the US might retain the militia system for much longer, possibly leading to a defeat (or at least not a total victory) in the Mexican-American War.
I can see two factors that might have tipped the scales. First would be John Adams winning the election of 1800. IIRC, he was more of an Anglophile than Jefferson. Perhaps Adams avoids a breach with Hamilton? A second factor would be a French refusal to sell New Orleans. I don't see it as implausible that Napoleon might refuse (or demand a price that the US couldn't pay). If that happened, surely someone would suggest taking New Orleans (and the Louisiana Territory) by force. The US couldn't face France alone, but if they allied with Britain, that would be a different story.
Obviously, the first thing that happens is that the US attacks New Orleans. I don't know how well defended it was, but eventually the Americans would win. Something like the Lewis and Clark expedition might happen, but with a more military bent, the aim being to secure the territory for America. The US might go after other French possessions in the New World. After or instead of this, the President (be it Adams or Jefferson) would probably send the US Navy across the Atlantic to fight alongside the British. This wouldn't have a major impact (the British already had a decisive naval advantage), but it would give the fledgling US navy some experience as well as letting them learn from the Royal Navy. Certainly the Royal Navy would come to appreciate the power of the American super-frigates. And if the US is allied with Britain, then there would probably not be any widespread impressment of American sailors. However, I honestly don't see the US sending much in the way of ground forces to Europe. Between all of this, we can safely say that the War of 1812 would be averted.
I can see a few long-term consequences. There's a minor possibility that the US takes one or more French colonies in the Caribbean. This might give the US a taste for colonial expansion. The US would also probably retain stronger ties to Britain, but probably not enough to have a major impact. The biggest change would be that without the defeats inflicted upon the US during the War of 1812, the US might retain the militia system for much longer, possibly leading to a defeat (or at least not a total victory) in the Mexican-American War.