I know this has been done a few times already, but I'm proposing a new twist. IOTL, Spain procrastinated until late 1802 in executing the Third Treaty of San Ildefonso to transfer Louisiana to France- and initially, one of the key components in Napoleon's planned treaty was the additional Spanish cessation of Florida to France, since it was acknowledged that without control over the Florida peninsula, Louisiana would be indefensible, easy prey for Britain or even for the United States.
As such, without the defensive lynchpin of Florida, Napoleon needed peace with Great Britain to implement the Treaty and take possession of Louisiana. But in early 1803, continuing war between France and Britain seemed unavoidable. On March 11, 1803, Napoleon began preparing to invade Britain, and resolved to sell the indefensible Louisiana Territory to the USA in order to generate war funds for the British invasion.
So, here's a slightly different WI- WI the French had succeeded in forcing the Spanish to concede Florida (East and West) to them as well as the Louisiana Territory, in TTL's version of the Third Treaty of San Ildefonso? As such, Napoleon deems his newly acquired territories in the New World to be satisfactorily defensible for the time being, and decides not to sell them off to the US of Americans after all. How would things play out?