1. An anarchic currency used in a different form of government isn't an anarchy the same way that china isn't capitalistic despite allowing the occasional capitalist endeavour.
2. Governments are already moving to regulate bitocoin
3. Bitcoin is not an anarchy, it is a democracy (not a constitutional republic in that if 51% vote to just steal money from X to give to Y it happens, there are no protection against it). Furthermore, unlike traditional democracies where people each get a vote, in bitcoin the vote is based on hashpower, which is extremely easy to centralize thanks to ASICs.