I think once the US ultimately ballanizes after the collapse there will be some establishing new diplomatic ties with the entities that emerge to control the countries that emerge from the rubble.
The actual state and how it’s structured is the problem, if the three west coast states decide to form Pacifica or whatever I doubt the EU is gonna spite the new country because of the American empire. Some countries will get along with the new Republic of Texas and other will prefer trade relations with Appalachia or Rustopia(parts of the Midwest)
I dunno how the chips are gonna fall exactly but I doubt the actual land mass and the people living there will be pariahs after the fall happens