You are kidding, right? If Coinbase stops trading in US this would be very bad for Bitcoin in the next 5 years at least. Practically every institution in US involved in Bitcoin uses Coinbase custody directly or via OTC desks. I just don't want to speculate what will happen in this case. I'm not a fan of conspiracy theories, but I sense a plot to harm Bitcoin adoption in USA and EU. First, they tried to shut down the banks that operate with the exchanges. This didn't work as they supposed. On the contrary they killed banks and their stocks, while Bitcoin was getting even stronger. They see the danger now - people and institutions prefer to buy Bitcoin instead of stocks and pull out their deposits. The same reason why China banned Bitcoin so many times. Being incredibly stupid it took them years to realize that neither regulations nor lack of regulations will hinder Bitcoin. So now they came with a btilliant plan - they started issuing fines with no explanations creating a delibarate regulatory chaos. This is like getting arrested and brought to court and the judge saying to you - look we are going to put you in jail because we have no idea who you are. But if you leave the country, we won't stop you. So, they play the chicken game. Bittrex shitted their pants at the first fine. OK, we can live with that. They are so small, nobody cares. But If Brian acts like a pussy too, this will have a major impact.
