The US would have a falling population without immigration so we'd be facing the Japanese situation of deflation and an eventual population crash (presumably).

The US would have a falling population without immigration so we'd be facing the Japanese situation of deflation and an eventual population crash (presumably). A lot of systems (pensions, social security, 401k, the stock market, most city governments and state budgets, et al). There would also be the economic slump as you remove consumers from the spending pool and labor from the labor pool. The massive gestapo/SS-like state apparatus required to round up so many people and deport them would take billions upon billions of dollars. It would also require shredding (what is left of) various constitutional rights and turn the US into a "papers please!" dystopia. This massive deportation police force would need to setup checkpoints on all major roads, in various public places, etc to even make a dent. Probably need to force all employers, even individuals hiring a contractor, to verify legal status. Outlaw cash to prevent paying people under the table too. The impact to US citizen children would be devastating; millions who were born in the US and are US citizens would be forced to leave and go live in a foreign country they've never been to (and in some cases barely even speak the language of). It would permanently alter their economic and development potential as they wouldn't have access to US culture, education, etc. You may not think they are citizens but you're simply wrong. Since the founding of the USA (and via common law) citizenship has been jus soli, confirmed by SCOTUS precedents too. If you're thinking of stripping their citizenship... trying to ex-post-facto do that on the basis of actions not taken by them and before they were born would require a constitutional amendment (besides being an immoral and shitty thing to do... We don't punish children for the actions of their parents; it's even in the constitution: No attainder or corruption of blood!). Oh and the fact that unless you're Native American you're a descendant of immigrants so it makes you a massive hypocrite and an arsehole?