Originally Posted by sirkonstantine

Its because of Preemptiveness (see https://en.wikipedia.org/wiki/Preemptive_war).

So, the US has floating, mobile airports so that it can strike anywhere in the world to prevent a larger conflict from happening. "Anywhere" means anywhere in N. America, S. America, Africa, Middle East, Europe, and the Pacific -- that's a lot of area if you think about it.
s.