Re: "to track money through the blockchain"
I have never heard of an assumption that there is a single, global blockchain.
Every instance of funny money has its own blockchain, I think that's pretty obvious.
However, even if I do not know how blockchain works, I do know that a blockchain is a public ledger, emphasis on the word "public".
So, as far as I'm concerned, all the police need to do is hire competent IT experts in blockchain and they'll be able to trace the money and shut down illegal operations. Or at least point the finger at them.
Now, as far as attacking anything abroad, I do believe that that puts the US in the same boat as the malware criminals themselves. Of course, it is expedient, but it is also not justified when you call yourself a democracy.
On the other hand, the US is no longer a democracy so, win all around ?