This is a false equivalency. The US government is allowed to regulate it's own money - that is - the sovereign currency that it issues. Bitcoins aren't defined or issued by the US government, so it has as much right to regulate Bitcoins as it has to regulate the Euro.
I believe your argument is flawed here, the US Government does regulate banks trading in the Euro if they reside in the United States. The fact they they are conducting business in the US gives them the right to do so.