Some of you are having the French and Indian Wars going same as OTL, and treating Louisiana as French. If the POD is after the F&I war, or results of ATL F&I war are the same as OTL, Louisiana is Spanish.
IMO, taking the OP at face value of ARW doesn't happen, and things are similar otherwise. There are PODs which could stifle the revolution, or kill it fairly quickly, but as OP said, doesn't matter, that's not the point of the thread.
As noted, if France avoids the ARW, the French Revolution may not happen. It is important to decide whether it does, or doesn't go off as scheduled. No FR/Nap wars means Spain is not torn asunder, and its empire remains intact. This means no Mexico as we know it. Louisiana remains part of New Spain, and continues a growth which sees it heavily Spanish flavored. I believe they allowed other nationalities to settle there, as well, so the colony won't be as Spanish as the rest of the empire. New Orleans was growing rapidly, and will continue so in ATL. Soon Louisiana will be too large to swallow. Spain will be careful to play nice on the Mississippi. Spain was growing careful about getting involved in wars, so there's no guarantee they get involved in the next major European War.
North America borders are pretty much set. The Nootka Crisis established northern boundaries, more or less. Britain might be able to push the boundary south a bit. The eastern border is set at the Mississippi. East and West Florida are British. The only way Britain gains more is through war.
The only way I see the lower 15 colonies (OTL 13 plus the Floridas) content in the fold is to grant limited autonomy. This new dominion may want a hungry land grab, but Britain won't want war simply for expansion, and will block this - until there's a major war with Spain. It will probably be 1820s or so before there's a real land pinch, much later if Canada is opened up, so there's no real need for a land grab. By then, Spanish Louisiana will be far more developed, even with minimal effort, than OTL 1800 Louisiana.
You can write your narrative any way you want in a no FR/Nap War scenario. I don't think we can predict the next major English/Spanish War. Sans one, Borders are set more or less at OTL 1763 boundaries.
With a FR/Nap Wars as OTL, Spain probably loses Louisiana to the British. Spanish California/Arizona/New Mexico/Nevada/Colorado/Oregon/Washington/Texas remains Spanish.
British NA won't be as expansionist at OTL USA.