"And the logistics, manpower, and time it would take to completely secure our massively long borders would make simply going to the moon look like building a barbeque pit over a weekend."
There was a time not too long ago that travel to the moon was a fantasy.
The answer is technology, applied efficiently, and supplanted with manpower as needed. The idea that you need one soldier per 50 yards to secure a perimeter is so 20th century mon.
Then I'll ask you the same question I asked earlier - "Name one society in history that ever completely secured its borders."