The US is richer, and has a larger GDP as of now (post Dollar run and Euro drop) than the European Union. The US has about ~40% of all private wealth (globally private wealth is around $270 trillion, with US households holding $86 trillion [1] of that; then furthering that are US corporate assets, which are far larger than European corporate assets).

By comparison private wealth in all of Europe is about $60 to $65 trillion. [2]

[1] http://www.federalreserve.gov/releases/z1/Current/z1.pdf

[2] http://www.reuters.com/article/2014/10/01/us-europe-wealth-s...