Oh they can try, but once it goes global, no one government can stop it.
http://www.reuters.com/article/us-russia-bitcoin-idUSBREA1806620140209
It's like Google, Facebook and Instagram , which are banned in here in China. People find a way to get thru. I need to use a vpn. Even For Steemit
But I do agree they can make it difficult. Here in China they prevented bitcoin exchanges to do RMB withdrawals
https://cointelegraph.com/news/china-bitcoin-exchanges-what-withdrawal-suspension-really-means-for-users
Or banks closing your account because of Bitcoin
https://community.coinbase.com/t/bank-account-close-because-was-using-coinbase-and-buying-bitcoins/12497
This one is not limited to US . The exchange I use in Singapore had to move thier bank account