The problem isn't foreign students learning to fly here. The real problem is:
1. A lose US immigration policy
2. Virtually non-existent enforcement.
3. Virtually no control even for those on "watch" lists and a politically correct (PC) mindset that says that even if the "threat" is primarily from those of mid eastern background, you can't scruntinize them more closely.
4. Idiots at flight schools that note VERY suspicious behavior, and do NOTHING. Again, this is probably due to the PC mindset and the fear that they'd be branded as "intolerent."
Time for common sense to take hold in immigration policy, cockpit design, and arming pilots for last-ditch cockpit defense.
Foreign pilots from friendly countries AND cultures, properly documented and monitored by authorities aren't the problem. Stupidity, incompetence, navity, and political correctness are. At least IMHO.