I don't think US government has come up with a proper news as on date. Same with China and South Korea. No government has not yet released any official statement confirming they will ban the crypto currency. However, if they do so, the market will receive a huge impact and the price will go down for sure for all the crypto currencies. I don't know on what basis you are thinking that the prices will go up, but I am sure the prices will come down as a lot of people will be selling their holdings to come out from the crypto market. It will increase the supply in the market, pushing the price down. No way the prices will be going up if US bans the cryptos.