Are there actions taken upon this matter by immigration?
YES a stamp that bars you from entering the USA for 10 years, which is really going to screw you over...who knows you might get a job with a carrier who flies into the US or one its territories, and now you have screwed yourself trying to cheap out by not getting a M1 visa.
I think there is another rule somewhere that states all flght training needs a m1 visa to be held.
goodluck, but dont rick getting the stamp is my thoughts