Nothing really. Companies like Disney outsource their IT functions to U.S. subsidiaries of foreign companies. But if you wanted to ban them then Disney could sign an agreement with HP or IBM and outsource their IT to a U.S. corporation...who will utilize their employees located in India or China. Either way the U.S. employee is going to get the shaft.
As I said in another post, if you want to continue to have a decent job in the US without getting outsourced or replaced by an H-1B applicant, have a DoD security clearance or be able to get one.