So whilst you can transfer money censorship free, you and the recipient need to then handle the transfer into and out of crypto which seems to be in many cases more difficult than actually transferring money other ways.
Not to mention the fact that that purpose is an astonishingly niche thing to want to do - at least in first world countries.
Are you suggesting crypto has no long-term value in the west?
Don't get me wrong. That vision of the future isn't here yet. Far too few vendors accept bitcoin today for it to be a viable closed loop system.
The most obvious way is to make it a crime to exchange bitcoin for USD, goods, or services. (Doesn't even have to be bitcoin specifically; they can say "blockchain-backed digital resources" or whatever.) Scope it under interstate commerce, in the US; who's going to stop them? Obviously that wouldn't kill BTC overnight, but it would kill any legitimate market. If they're really worked up they can compel financial entities to disclose or block payments to/from known BTC exchanges, or compel telcos to do the same for blockchain mining traffic. They could even ban owning bitcoin; delete your keys or you're committing a felony.
How wouldn't they ban bitcoin, really?
In that scenario I suppose bitcoin's only hope would be that the countries of the world wouldn't coordinate to enforce a global ban. Seems unlikely that they would. But, back to your point, a total US ban might be enough to eventually kill the ecosystem.
Step 2: make use of Bitcoin illegal. You know, "ban" it. It's a plaintext P2P protocol, not exactly magic. If you control the network, you can identify Bitcoin nodes and charge their owners, exactly how law enforcement can enforce laws against other illicit P2P traffic. This would drive any remaining die-hard users to services like Tor.
Step 3: if Bitcoin is somehow still popular enough to be considered a problem, block Tor.
“One has a moral responsibility to disobey unjust laws.” ― Martin Luther King Jr.
So, how does this work if I'm, say, trying to support the protests in Iran, who just shuts the internet off?
>but isn't centralized wallets/exchanges like coinbase defeating the entire purpose of crypto currency
This is true. This is my biggest problem with the current ecosystem. If history is any guide, they'll eventually suffer from some sort of scandal and/or run that drives customers to a superior competitor. This only kicks the can, I realize, and is far from the original vision. But at least each centralized service learns from the costly mistakes of previous ones.