President Trump says he wants to use military to secure US-Mexico border

The US/Mexico border is among the longest non-militarized frontiers in the world...

We can fix that...

All he needs to do is see if any veterans want to do the job.

I concur with your assessment SSG(P) (Join to see) it makes great sense to guard our southern border IMHO terrorists, terror wannabes, coyotes and gang members such as MS-13 are certainly threats. I expect that NORTHCOM will have overall command authority and the actual troops with be National Guard - Army and Air Force service members.
FYI COL Mikel J. Burroughs LTC Stephen C. LTC Orlando Illi LTC (Join to see) LTC Ivan Raiklin, Esq. Maj Bill Smith, Ph.D. Capt Seid Waddell Capt Jeff S. CPT Jack Durish MSG Dan Walther MSgt Robert C Aldi SFC Stephen King MSgt Danny Hope SGT Gregory Lawritson Cpl Craig Marton SP5 Mark Kuzinski SGT (Join to see) Maj Marty Hogan