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.