If the government wants to tax bitcoin, then I think they will put the tax on the people who verify the transactions(miners) and in turn the transaction fee will now include those taxes.
That is not in the protocol and not going to happen. In the U.S. taxes are, and have always been, an obligation of anyone who profits from bitcoin. In fact
ANY PROFIT YOU MAKE FOR ANY REASON IS TAXABLE. It is not on the miners, it is on you if you made a profit.