So, I started a game as 1792 Ottomans and USA formed Vermont

[FantasticFwoosh]

Some of the mentioned problems can be blamed on that, but the AI preferring Vermont over the USA is likely a problem independent of start date. IMO since end game tags are a thing the USA should be one. Either that or they should be banned from forming individual state tags. That makes no sense at all. One state would not be able to gain control of the entire Union without some kind of military struggle.

Obviously this would call for the USA to undergo a rework where they become the Mughals of every pseudo state on the American continent rather than a single-tag.

The American Republic govtype doesnt need any especially required rebranding for this, other than maybe porting the American Dream dlc into vanilla or FLC to enable the governement type.

 

[Idle America]

This is known, later start dates are not supported anymore and it has been stated many many times.

"What do you mean? Giving the US over a dozen generals in 1776 when the limit is three makes perfect sense!"
-Paradox, probably