Americans have a a sort of circular view of Europe's defense..the idea that America defends Europe therefore Europe should pay much more than it does for its defense so that America wouldn't have to spend as much to defend Europe. 

The problem with that view is that it is based on a faulty premise.  America doesn't defend Europe in order to ideologically promote a free Europe, it spends money on defending Europe as an extension of US direct foreign policy against Russia.

America spends money on military defense in Europe to support American military dominance over Europe, a direct policy goal of the US ...which Europeans have grudgingly allowed since the end of WW2...out of necessity in the cold war period of Russian military threat and expansion, and now, in the post cold war period of a preference for social welfare expenditure over expenditure on a pan-European defense by Europeans.