Contributions by international scientists and engineers to the U.S. workforce have long been taken for granted, after all the U.S. is the leader of the free world and the conditions to conduct business and do research here are the best. Ever since 2002-03 the number of new enrollments at U.S. higher education institutions has been stabilizing after a sharp decline (Institute of International Education). This number only accounts for students pursuing bachelors or advanced degrees, not post-docs who are equally if not more crucial to the creation of value and knowledge in the U.S. economy.
Is the shift of perception and the subsequent decline in applications of international graduate students following the shift in policy reversible or is the U.S. slowly losing its position as the globally dominant R&D nation? Even more troubling perhaps is the decline in the number of international post-docs in the U.S., currently ~60% of all post-doc positions are populated by international post-docs staying between 2-4 years and it is them who, arguably, drive scientific discovery. Renewing visas or even getting them in the first place has become a problem for post-docs as well, again a troubling trend for the very early stages of the value creation system.
One can argue that a change in the administration will bring about a change in public perception abroad, but visa regulations are not likely to be relaxed anytime soon. So it remains to be seen if the U.S. can maintain its position as the global research center, but if it doesn't things will go from bad to worse, as it certainly isn't the manufacturing center of the world and will most likely be eclipsed by China and India in terms of imports in the very near future. One can only hope that policy will not lag too long behind reality.