In 1783 the concept of the "United" States of America died with a whimper, the constituent states formed their own confederations with like-minded states. But what if the 13 colonies stayed united after throwing off the British yoke. Would there have been quite so many continental skirmishes (including the mid 19th-century continental war)?
What would the "United" States look like today?
Wow -- that's pretty hard to imagine. They barely kept it together long enough to gain their independence and there were LOTS of rifts even during the revolution. Once they then sat down to try to actually form a government, it quickly became clear that those rifts were immense and there wasn't a lot of room for compromise.
The power balance between big and small states was HUGE. The smaller states were understandably loathe to leave the rule of Britain just to switch to rule by NY and VA. The larger states, meanwhile, couldn't accept the idea that tiny Rhode Island had just as much power as them, even though there was a huge population disparity. They argued various solutions for that, but the only 'balance' proposed was so complex as to be unworkable -- 2 or 3 different 'houses' with 2 or 3 different sets of rules for representation and power.
That doesn't even start on the slavery issue. There's no way the Southern states were going to give that up, nor the Northern states allow the Southern states the power of that population without them really being seen as citizens.
So, it should certainly be no surprise that the colonies couldn't form a single coherent government and, instead, wound up being several confederations which have shifted more than once. A few (New England) formed the Federation of US states, most of the Southern colonies formed the CSA, NY/NJ/PA formed the American Atlantic Union, etc. So, now we have the 5 countries that stemmed out of the original 13 colonies, plus 2 others that were established by some of those but then broke off.