The method of tax collection is not the problem as the amount of taxes collected will remain roughly the same. The real problem is spending and Congress’s ability to have unlimited borrowing.
This is why I think that Cruz should drop out, endorse Trump and challenge/unseat McConnell in the Senate. He’d accomplish much more their. Trump can then appoint him to the Supreme Court before leaving office.
Economically, you're correct. But in terms of psychology, having the tax be visible on every purchase will at least make the average non-political type acutely aware of the cost of government.
Remember, a lot of these folks see their income tax refund as "free money". Got to change their perceptions to get enough popular groundswell to do something about all that spending.