The only countries that are banning bitcoin and other cryptocurrencies are those that have capital controls - like China, which is experiencing capital flight.
The USA does not have capital controls, and has nothing to fear from bitcoin, and quite a lot to gain from it (new asset, new technology).
The USA DOES have capital controls. Many banks, like in Hong Kong for example, rarely allow Americans to open accounts anymore because of FATCA laws and all of the compliance overhead that it brings.
The USA, or individual states, can order banks to refuse remittances from exchanges at any time. I remember reading that Wisconsin and possibly residents of another state are not allowed to open accounts on US based crypto exchanges. New York drove out most crypto enterprises due to regulations.
If Iran and Venezuela get their cryptos going, expect enormous headaches for crypto in the USA under the guise of fighting terrorism and don't expect much of a warning when it happens.