The transatlantic alliance is the pillar of the EU’s foreign and security policy.However,as major readjustment happens to US foreign policy,EU-US relations undergo significant changes,and there are also tendencies of readjustment of EU’s foreign policy.A“Different”America Since the World War II,Europe has been in close alliance with the US,by which America provides Europe with security protection,and Europe willingly follows the US leadership and sits at its feet on all major global diplomatic and security issues.However,since taking office,the Trump administration has pushed forward the“America First”foreign policy,and made America no longer the same country as Europe used to be familiar with and trust,but conversely the biggest saboteur and violator of European interests.