You can't surveil foreigners/travelers/etc. without surveilling U.S. citizens. Most people should know that by now, and if they don't, it's because


I will pose a [used to be] "Republican Platform" question:
What business is it of yours?
Did you ever stop to think that perhaps some come here to escape persecution, and maybe their laws are so draconian that they are considered criminals there, but not here? If they have some kind of trumped up charge/record, should it follow them for the rest of their lives? Even up to including defending and protecting themselves and/or their loved ones.
Or maybe they simply want to stay and visit for a while before going to the next country to enjoy/explore? Or maybe the workers work the fields/ranches that Americans don't want to do, and if they can scrape by with an income they won't have to resort to "crime"?
We have what are called the Bill of Rights. Included in that are due process rights. Read them sometime. That's not to say that if someone commits a legitimate crime here that he/she shouldn't be held accountable. But it should done on a case by case basis, the same way as if an American committed a crime and you wouldn't want to be blanket labeled.