From what I’ve seen by actually teaching at the college level part-time, its poor K12 preparation and a culture of laziness not a sense of unfair competition from foreigners that discourages Tom, Dick\Jane & Harry USCITs from STEM careers.
By the way there’s way way more to STEM then network engineering!
My experience is similar to yours. It’s one thing if young people steer clear of STEM fields because they are concerned about foreign competition suppressing wages, but then what fields ARE these people getting into?