The main problem is that in the US, it is nearly illegal to engage in a private, anonymous financial transactions - whether in Bitcoin, Dollars, or anything els

The main problem is that in the US, it is nearly illegal to engage in a private, anonymous financial transactions - whether in Bitcoin, Dollars, or anything else. There is a loophole for small transactions in paper money, but that loophole is slowly being closed. This is not a technology problem. It is a policy problem.