It is more complicated than that. For example: bombings in Madrids. Would the Arab savages have targeted Spain if it wouldn't have been allied with the US? And what about stupid American ideas like the wars in Iraq and Afganistan? This is all included in beeing "defended". That beeing said, I aknowledge the gist of your argument: Europeans have choosen to be "defended" by the US so they shouldn't complain about the bill.