Reagan is to blame just as much as any other Pol, yes. Only argument he could have used really was the Cold War was still going so hard to bring the troops home.
Now, for the past 3 POTUS, there is no excuse to have troops stationed on our southern border, with authorization of deadly force if apprehension is not possible. EU, South Korea, etc. can protect themselves now. They've got all the tech and manpower needed, along with plenty of satellite power to detect large scale movement, to be aware of an organized attack and respond to it.
No valid reason at all for our southern to not be secured by the troops we're already paying for, the equipment we already have, etc. It'd be great practice for them, and, way better when they want to be on leave or we need to move them around. It's a multiple win, with no loss (well, loss on our side...which as a country is what we should be concerned about).
Chuck