The US had a lot of interest in it for one huge reason. New Orleans. Almost all of the commerce in the South, especially in Tennessee, Kentucky, and the territories acquired from Spain that would become Alabama and Mississippi passed through New Orleans. When the US got New Orleans, they got a huuuuge boost. So, if Louisiana territory is for some reason up for grabs, New Orleans will be taken by the Americans.
But if it remains French, then Napoleon could either A) Make a close friendship with the USA to ensure not having to deal with a war there, and maybe get some extra help against the Brits, or B) Wage war in the Americas and further expand the French Empire there (which was one of Jefferson's principle fears). How that would turn out is hard to say. The US had no standing army, Spain was controlled by France, so that's in France's favor in America, but the French were also very tied up in their wars in Europe, plus British Canada might swoop in on the French territory. If the French do hold it, they may end up looking to retake Haiti.