The USSR would span its territories in the 80s but be led by a competent Marxist leninist party. Same for the Warsaw pact countries and Yugoslavia. These were caused by revolutions popping up all across the globe and other areas.
The US choice would have itself devolve into chaos while its power and influence decreases. Infighting would break the US into pieces but territories like hawaii and alaska would gain independence. The main government would be torn asunder and the CIA rogue and unfunded.
If ‘collapese of the American Empire’ includes their losing access to nukes, then that one.
It’s already happening. The US is already unravelling. The question facing humanity is not whether or not capitalism is ended, it’s whether or not a nuclear war happens as capitalism ends.
Plus, the USA existing is the main barrier to anything like the USSR making a comeback, whether that’s in its original form or more likely a Socialist bloc rising out of Africa, South America or West Asia.