What lives exactly do you mean? Because there's nothing unique about America that plenty of other countries don't have anymore, and most of us manage to spend considerably less on defence than America.
Those countries manage to spend less on military than America, because of Pax Americana. This is a uniquely peaceful and prosperous time throughout history where there has been a liberalist unipolar political climate worldwide because of the USA, and dozens of countries have taken advantage of the fruits of America's defense labor - while chipping in little for themselves, and others, in return. America has had the strength and posture to hold the entire Western world on its behalf, and did so.
Europe is re-arming, one of the two leading candidates for this election cycle are Anti-NATO. Expect this generations-old luxury for other western countries beyond America to soon change.
Europe is re-arming, one of the two leading candidates for this election cycle are Anti-NATO. Expect this generations-old luxury for other western countries beyond America to soon change.