Today, radical liberals have the public ear: the Democrats are in favor now, but the Republican opposition holds a large clout of power
What you call "radical liberals", i.e., liberals who go back to the root, is better known as "classical liberals" or "libertarians" in the US. Classical liberals and libertarians are split between Republican (nominally laissez-faire) and Democratic (nominally socially liberal) parties, although they have recently been leaving the Democrats, given that the Democrats seem to have given up on socially liberal policies.
Yes, and this will be a conservative vs. radical argument as always, with conservatives who want to take it in small increments, and radicals who want to slash it all and implement a 9-9-9 plan
I think a 9-9-9 plan would probably be better than what we have now, but it has no chance of passing; even if it did, it would be destroyed by the process. Also, rapid change, even for a better system, often ends up much worse in the short term.
I think what is politically feasible and much better to deal with is crafting exemptions and let people vote with their feet. Imagine creating corporate tax havens within the US to compete with Ireland, or greatly loosening restrictions on tax free retirement accounts. If you look at the history of social and political change in the US, we often haven't bothered with repealing old laws, and instead just made them irrelevant.
There will come an age when America either collapses or finds itself tired of running radicals against radicals, with the alternative of up-and-coming radicals.
I wouldn't be so gloom and doom about it; for all its problems, the US is doing very well, both compared to its own history and compared to other nations. It takes more than a Bush and an Obama to get the US to collapse.