Let me be clearer.
I think they are going to say : all blocks mined in the US MUST build on an OFAC AML KYC compliant chain. No mixing allowed, no anonymous txs allowed.
That's a de-facto fork.
Then BlackRock uses that fork. Coinbase too (by extension). And then they say : exchanges that deal in something else than our fork are dealing in shitcoins and that's not allowed.
So to transact with these entities, you must use a KYC/AML enabled wallet.
That's the attack I envision. The bill is a clue in that direction.