Two points:

- Government agencies can ascertain the identities of virtually all accounts with Chainalysis, following the money to the fiat entry/exit points.

- Even with a theoretical anonymous account, with centralized stablecoins like USDC or USDT, the balance held by that account can be frozen because the issuers of those tokens have crafted their token contracts such that they maintain the ability to mark certain addresses as incapable of transfer