You have to be careful with a country. Even a nation as vast in size and huge in population as the United States cannot be endlessly experimented upon. You cannot just leave borders open, or allow in large numbers of people with totally different value systems from your own.
That is the mistake many European countries have committed in recent years. They have opened their homes up to people from almost every part of the world where there is civil strife, war or just a lower standard of living.
