Nope Bitcoin can't be outlawed by the US government because there are several companies in US that are involved in bitcoin which have gone public. For instance gray scale Bitcoin trust holds the largest Bitcoin in the world and it's a US company,even rothchild family are investing in great scale including top men who are also involved in bitcoin. Therefore banning Bitcoin in the US will have a really negative impact on their economy,the government knows this and won't want to make any move that will affect their economy negatively