Just as a thought experiment: how would the US gov actually go about making it illegal to use Bitcoin, or "ban" it? You obviously can't shut down the protocol itself. Maybe you go after the exchanges and treat them as if they're the drug dealers, if you were to "treat Bitcoin as a crime" (and by that I mean making exchanges or possessing a wallet).
People will use dogecoin then, so the law will probably refer to "cryptocurrency". Which will not be easy to define and will probably get other centralized currency schemes in trouble as well.
Any other ways hypothetically speaking?