The system will adapt. It will be a painful experience, but eventually they will have no choice. There are examples to that on the course of history. For example, the Romans arrested and executed Christians for nearly 300 years, but failed to stop the ever expanding adoption of the new religion among the enslaved nations. At the end, the empire adapted - Christianity became a must if you wanted to have any influence in the Roman society.
http://en.wikipedia.org/wiki/Persecution_of_Christians_in_the_Roman_Empire
As to taxation, there are alternative ways. One is voting for your preferred party with money - e.q. you give them enough money for 4 years, instead placing a vote.
I agree, with your assertion that the system will adapt, but the question is, which system? decentralized (bitcoin) systems adapt much faster than centralized (govt) ones.
So, the govt places a tax on US exchanges, and everyone starts using non US exchanges.
Look at what happened to the Roman Empire once they started adapting to Christianity...