The United States, obviously. The US is still occupying Europe with hundreds of military bases, it supports and funds terrorist groups and drug cartels, it undermines democratic governments and threatens the security of Europe's people through NSA and CIA sabotage.

There's no reason for the US to maintain the overwhelming global military presence that it does, particularly in Europe. World War 2 is over, and the US will never actually go to war with an enemy like Iran, Russia or China, or any country that might actually pose a legitimate threat to global security, so why keep up the pretense of being the "world's policeman?"