I mean, when Mars gets colonised, what's to stop Mars from becoming a superpower in the Sol system within a very short period of time? Pretty much nothing.
Once humanity gets its footing on Mars - and it really looks like this is going to happen within the next few decades - there are going to be security repercussions for those of us left on Earth. I believe this Space Force effort is an attempt to make USA not only Earth's police force, but that of the solar system, too.
Extraordinary times! To be actually typing this, in earnest..