It seems like it would be a lot easier to just shut down the USD-BTC exchanges. If people can't get money in or out of the system they don't need to worry about what happens inside the system. (I'm ignoring mining, since there's a serious limit on how large that can get.)
Not necessarily. If it became apparent that people could pay each other in bitcoins without being taxed, there would, eventually, be no point in have USDs at all.
