Focusing solely on the land itself, and not the butterflies caused from Napoleon having less funding...
For starters, Mexico was still under Spanish rule, albeit with insurgents running amok. Secondly, the Americans would likely still be at war with the British. Anyway, Louisiana would be given back to the Spanish, but the British could possibly haggle for it.
If the Spanish got it back, the Americans could follow what Jefferson thought would happen, in that Louisiana would slowly gobbled by the Americans. If the British got it, either a longer War of 1812 (because Clay could argue that you know, why not guys) or the Americans trying to get the land later, when the Manifest Destiny is raging harder.
In other words, the Americans would be keen to try and get it still.
