For (2) - obvious answer here is crypto but again, the crypto market might implode because if (1) actually happens, the US gov is extremely incentivized to make crypto ownership and trading illegal.
Crypto may be a bad bet in a world where the dollar implodes. If crypto is predominantly healed by dollar holders - rebalancing from crypto to the dollar denominated assets they need to function could harm crypto prices.
Alternately, in the event of a dollar default - the world may not be conducive to the capex+energy expenditure required to mine crypto. If interest rates went to 20-30%, I’m not sure that crypto mining would be a viable concern - causing instability throughout the crypto world.
That being said, whether crypto is a good hedge or not really depends on whether it’s worth putting money in today - regardless of the potential for US default. Particularly in comparison to Yen, euro, and yuan assets.
If the US government outlawed crypto to save the USD, they'd have to also outlaw gold, because that's where all the money would flow to instead. The rest of the world wouldn't outlaw gold and crypto, so the effort to kill alternatives would fail and it would just accelerate fleeing USD into gold and crypto.