All transactions are public. They could see where your Bitcoin went and also blacklist that address. No one would want to risk transacting with someone who was blacklisted.
This is why the whole argument about Bitcoin being an asset out of reach of government persecution is totally nonsensical. Anyone making that claim is either ignorant of the public nature of the Bitcoin blockchain, or is woefully insouciant in regard to the power and reach of a sufficiently motivated government. It is particularly easy for governments to crack down on anything related to banking, finance and currency, as they already have vast control and influence in these areas. It's true that governments cannot kill Bitcoin outright, but they could make it so prohibitively difficult and essentially pointless to use that there would be no reason to own it. And they could do this overnight if they so chose.
Honestly, at this point I believe that the only reason Bitcoin is still allowed to exist (especially given the massive fraud taking place with Tether, and the entire nature of USD stablecoins, which are blatant tools for tax evasion and money laundering) is because the U.S. government itself (and perhaps other governments) are using it to move money around off the books for various shady purposes (i.e. Ukraine payoffs, laundering CIA drug money, funding various black ops outside of congressional oversight).
As far as I know, no wallets look or care about “blacklisted addresses”. Maybe exchanges could do this, but individuals don’t care…just do a coin join and be done with it. Iran is still mining bitcoin, they haven’t been “blacklisted”