In simplest terms, none. No policies made the difference. The reason the US began (and has now stopped) coming out of recession, and europe has continued to decline, is that in europe, the protestant germanic states are unwilling to subsidize the catholic mediterranean states. In the USA, this same anti-subsidy conflict is conducted along racial and urban rather than national lines. The difference is, that in the USA, we are powerless to stop that subsidy because the monetary and fiscal power is centralized, and the government can inflate away debt across all people, whereas in europe the EU cannot inflate debt away because the monetary (central) and fiscal power (local) is separated. However, there is very little difference in practice. In the States we are a polarized society, and in Europe they are a polarized society. So, the difference in the duration of the recessions is structural, not one of policy. This is why the left economists favor centralization and the right economists favor breakup of the eurozone by german exit: its a moral conflict.