There is no invitation to join - you inherited the citizenship. You may not agree with where the money goes but its up to you to change the system. There isn't really a way to opt out/move away but that's the limit of the analogy rather than of the logic.
Isn't that the problem libertarians are trying to find a solution for? Is your agrument now "there are no libertarian places out there, you live in a Democratic government society, so just buck up and deal with it?"