The United States boasts the largest gross domestic product, so it makes sense that The United Sates also spends the most on "National Defense". With more countries either obtaining a nuclear arsenal or approaching the ability to generate one, it is imperative for The United States to continue to build and update missile defense systems and maintain strong nuclear offensive capability to be able to respond to any threats.
People think that nuclear warfare is the line no one will cross, but they are wrong. People are as ruthless as always, and someday, the big red button will be pressed. We can prepare for this day and shield our major cities from missiles, or we can sit by and wait. "Nuclear Tension" is what Russia calls it because they can't develop something as well as we can. They want a fair war. War is not fair. If you have a gun, we have a tank. If you have a machine gun, we have a 3000 pound bomb. So if you enter nuclear war with us, we will block the blunt of your attack and fire back with twice as many.