I got it from two places:

1. Watching the standard of living in the US outpace the EU for decades and comparing their economic systems.

2. Basic common sense tells you that you need resources in order to fund a welfare state, a long list of positive human rights, and all the other things that the EU states want to do. Money buys resources, especially when you don't have direct access to them (which is the case for most EU states).

Probably one of these scissor statements where economic leftists think that obviously the problem is focusing way too much on [X] and the others saying the problem is focusing far too little on [X].