If the untoward event is solely in USD, perhaps, but not if it's in crypto. Exit scams, hacks, rogue employees, etc, could still hit a US exchanges' crypto holdings and the government probably cannot or will not compell a roll back, supply expansion, etc, on a major blockchain.

If anything is actually protecting clients against crypto theft, it's the exchange's privately-purchased insurance rather than the government. Although I wouldn't rely on that for much either as insurers are rarely eager to pay out.