Of course the idea of progressive taxation is a pernicious one (see http://scholar.harvard.edu/files/mankiw/files/defending_the_one_percent.pdf), since it punishes success, but for those doubting that the US is, in fact not just in word, a progressively taxed nation, here's the cite.
That all being said, there really are two axes of argument here – one, should taxation be progressive, rather than equitable, and two, should government be larger or smaller. You could make the argument for a progressive tax system that uses much less revenue, and you could make the argument for a regressive tax system that uses much more revenue (as apparently many of our european socialists do).
I like to think of government the way Clinton thought of abortion – safe, legal, and rare.
Compared to peer countries, the U.S. taxes the rich quite heavily. But it doesn’t spread what money it collects as equitably.