Interesting question from this tweet I never thought about seriously. Unlike the USSR, the US doesn't have 'its Russia', the dominant sub-entity that would inherit all of the nuclear weapons.
If the US collapsed like the USSR, which looks more likely by each day, they are the USSR 2.0 in all characteristics, so what would happen with their 5000 nuclear warheads arsenal?
Imagine those 50 states (or if some of them form smaller federations, then less than 50, but still numerous) each having a part of that arsenal, it would be crazy.
So, after Civil War 2.0 ends, maybe China should first ask for all those nuclear weapons to be confiscated before starting to give them BRI loans for recovery individually.
China, Russia, and Brazil, the top seats of the new international organization could start putting sanctions on those new rogue countries out of 50 who refuse to give their weapons away.
No trade, no investment, no finance, no loans, no weapon procurement for any of those states that refuse to get their nuclear weapons confiscated.
The new top security body of the world, of China, Russia, India, Brazil, South Africa, the former BRICS could then divide those weapons amongst themselves for disposal.
Also, the US debt to China is still 850 trillion $, so China should have all the legal and moral rights to confiscate all the assets that they like after the collapse to pay that back.
Some states that cooperate with China well, get their 'protection' against other neighboring states. China and Russia could even turn them against one another to control them better.