The US government doesn't care which stablecoin will be popular. According to statistics, USDT and USDC are backed by US treasuries, about 80%. The US government is not responsible for the risks of the stablecoin issuer.
Of course, they’re not responsible since it’s already the user’s mistake. But the fact that they’re backed by US Treasuries is their way of ensuring that USDT/USDC issued are backed by real money. That means users don’t have to worry about their holdings losing value in the future due to scams from the issuer, because in this case, the government will ensure and protect users from that possibility.
What you write sounds very nice, but in practice, the state is very reluctant to give money back.
Look at the practice of the FTX or other exchanges: reimbursements take years and are accompanied by very complex bureaucratic procedures, as a result of which it is cheaper for small investors to forget about their losses.