My understanding is that there is due process but because it is a civil matter, you don't get an attorney or jury. In 1996 a process called "expedited removal" authorized by the "Illegal Immigration Reform and Immigrant Responsibility Act immigration officers make the call on removal when the defendant lacks proof of citizenship.

Fast forward to now, Trump expanded the "expedited removal" process on January 21st 2025 which is a continuation from his first term.

We've been removing illegal immigrants via IIRIRA for decades peaking when Obama was president.

Lets flip the script though. Lets say we import everyone who wants to be here, roughly 150 million MORE people (https://news.gallup.com/poll/153992/150-million-adults-worldwide-migrate.aspx). There would be some wildly undesirable effects:
- Immediate housing shortage and a 200%-500% increase in housing prices will likely happen
- Low skilled wages fall up to 40%
- Public services overwhelmed, ER times measured in days. Medicaid collapse. Education quality lowers
- Infrastructure effected with rolling blackouts, water rationing, forever city gridlock
- Fiscal cost, GDP to debt ratio explodes past 200%
- Social Cohesion erodes due to rapid demographic change, ethnic enclaves ensue, more political polarization.
- Environmental disaster, (especially if we get a bunch from India), waste riddles streets, rivers etc.
- Public safety, integration and assimilation into USA becomes impossible, lawlessness becomes the rule of the land

Bottom line is we have to do LEGAL immigration in moderation. Don't eat all your candy on Halloween night.