Don't go there right away. While we need to close the border and protect ourselves, the vast majority of these folks that come here just want a better life and are not looking to harm anyone. Also, I hear they vote Republican.
On the other hand, it only took 19 to do the damage they did on 9/11.
You many now proceed to FULL PANIC MODE.
Say on the anniversary of 9-11 we had a LAX style terrorist times a thousand -- all at once killing as many random people as they can. With an unarmed population and no Israeli security to protect us the death toll would be insane.
Of course the FBI would report the thousands of isolated incidents were just a coincidence along with the date they all independently decided to "get despondent." And only those guys they had a file on would be counted as terrorists.
Yes and some don't even intend to stay permanently in the US. I think for those who are really here doing certain jobs and not using fraudulent documents and IDs, there should be a guest worker program set up that makes it so they don't have to be illegal and can be screened before they come here. Some of those farm workers, maids, and gardeners are decent enough people, they don't need to be given citizenship but they shouldn't be treated like vicious criminals.