I imagine the US government will take this as cause to further clamp down on exchanges and other Bitcoin services. They'll push for stricter regulations and enforcement under the guise of concerns over sanctions.
if they do it they will only use it as an excuse but the real reasons would be different. these sanctions didn't start yesterday, they have been there for years and no Iranian could ever use any of the bitcoin exchanges since none of them ever accepted them anyways!
The sanctions didn't start yesterday, but the Treasury Department has been slowly ramping up its pressure on exchanges ever since 2017. A formal endorsement of mining by Iran suggests there will be increased Iranian capital flow into mining. Between that and the fact that
Iranian officials have repeatedly said cryptocurrencies can be used to thwart sanctions, it makes sense that US officials are watching closely. The fact is that P2P markets, DEXs, and non-KYC exchanges could theoretically allow circumvention of sanctions.