Not saying you're wrong, ukanon., in fact it is a logical scenario. But I'm guessing that you've had a couple of bad days and imbibed too much news.
Economic collapse is very, very possible - the whole 'recovery' is based on an optimistic 'debt bubble' as far as I can see. In that case would anyone want to immigrate though? Certainly uncontrolled immigration would bring about civil wars, but I can't see even the nuttiest government using it as a deliberate tool for control - look at the problems they'd be left with!