Yep. As I told people in the bitcoin space years ago, the Roman Empire and Ghengis Khan and Imperial Britain all existed with decentralized, fungible, untraceable money called "gold and silver coins". That didn't prevent the State from existing or collecting taxes or imprisoning people or enforcing its sundry laws.
Bitcoin may change things, possibly a lot, and maybe for the better, but you have to be realistic about how much change is actually feasible.
The current governments exercise a lot of power through the banking system because it's convenient. If Bitcoin (or some more private successor like Zcash) makes the whole finance sector "go dark", like "Tor for money", those governments will still be there doing their thing, just using slightly less convenient methods.
I like how you mention two technologies that governments created.
1. Gold and silver coins were created by governments.
2. Tor was created by the government.
When you convert USD to bitcoin, that USD doesn't disappear, it still exists in the private sector economy. Nor does bitcoin increase the money supply of USD. That supply is controlled by the government.
What happens when the IRS cannot tax the bitcoin transactions is that more USD remains in the private sector than normally would. This does not cause financial problems for the government (Since government makes USDs anyway).
More USD in the private sector means at worse rising prices, and at best an economic boost.
Bitcoin may change things, possibly a lot, and maybe for the better, but you have to be realistic about how much change is actually feasible.
The current governments exercise a lot of power through the banking system because it's convenient. If Bitcoin (or some more private successor like Zcash) makes the whole finance sector "go dark", like "Tor for money", those governments will still be there doing their thing, just using slightly less convenient methods.