U.S. President Donald Trump's criticism of NATO over Iran has escalated into a crisis within the organization, following criticism from European countries over its mission and potential withdrawal from the alliance. The comments have raised concerns about the U.S.'s commitment to defense of European allies if they are attacked, regardless of formal separation. The alliance, which has been crucial for European security since its inception in the Cold War, is fraying and the mutual defense agreement at its core is no longer considered a given. The White House has responded by saying it will remember the United States for its time as a matter of concern. The tension between the United Nations and the United Kingdom is causing concern for the NATO alliance.