There are, and should be real-world limits on the ability of the US government to stop things from happening by deeming them illegal.
In the case of Wikileaks, one such limitation is the relatively decentralized nature of the internet. The US government was able to pressure Amazon to refuse to host it, but was unsuccessful in pressuring OVH, so Wikileaks remains online. There is no Great Firewall of America, so it remains accessible within the US.
Another limitation is that while the US government can and did pressure Paypal to refuse service to Wikileaks, there's no equivalent for preventing transfers of cryptocurrencies.
It already exists: the legal system.
> there's no equivalent for preventing transfers of cryptocurrencies
Money laundering, child trafficking, drug profiteering, terrorism etc. they all come with costs.
And doing nothing to stop them is not good for anyone.
And so the issue you have is not with Paypal, Visa etc unless you think that those payment companies should tolerate illegal parties transacting money. Because that is a very slippery slope especially given how much wealth in the world comes from the despair of the very poor and helpless.