Any proper response about the difficulty of assimilating certain peoples, the desire of Muslims to conquer, or the piss poor job Americans did assimilating immigrants who came from 1840 onwards would either get me banned or end my life in politics.
On the other hand maybe a failsafe device like a Cobalt encased thermonuclear device is something we should consider deploying, not to launch at anyone else, but rather to detonate here. If they are going to take us, we can at least leave a barren land where cokcroaches will even refuse to inhabit.