I think he might be worried the US could go the way of Nazi Germany who was destroyed by rampant, unfettered illegal immigration. In a few short years immigrants - who not only didn’t speak a lick of German, but had no interest in assimilating - streamed into Germany from places like Russia, the UK, and even America. Risking long treks on foot in the snow, or in small, rickety boats across the channel, they overwhelmed the physical barriers at the borders and almost immediately began a series of violent acts that eventually lead to the downfall of the German government. Some real bad hombres.
It really is a cautionary tale if you think about it.
