Réponse :

America was the opposite of what it is today. The borders were fully opened and this was the epic period of the american dream. But for political, economical and security matters, things changed. The frequency of delinquency, drugs imported illegaly and terrorism became impossible to fully control through the traditional ways. America changed its strategy and tends to close everything to itself, not only the boarders. And this is part of the political reason, this new vision was introduced by president Trump.