Of course it exists. It's called an I-94. DHS has that info.

Every single foreigner is assigned a unique alien number and tracks your entry and exit into the country.

They just don't want to deal with connecting information from two different departments.

Strictly speaking that's insufficient as crossing from the US into Canada by land doesn't invalidate your I-94. They do need to join it against a bunch of other data -- which they do have.

Exactly. They have the data, but they’d need to link it to a few other sources for it to be complete.

The US, unlike Europe (at least in my experience) doesn’t check passports on the way out. They rely on flight manifests or information from Canadian authorities on who has exited.

> unlike Europe

Unlike the Schengen zone, certainly, but some European countries also do not check passports on exit (the UK is a good example).

Bosnia just waived me on when I was crossing through from Croatia. Checking a whole buss must have seemed like too much effort

Yup. It was Schengen in my case.

With so many types of data collected, one shudders to imagine what will happen if they discover the join sql statement.

When did they add the join statement to COBOL?

So when a H1b holder enters the US with their H1b, there is no way for the border official to know if it's real? That seems impossible to me.

When you enter the country on an H1B or otherwise do anything related to any visa status, the onus is on you to carry around all relevant and supporting documentation, in physical, original paper form. Visas, passports etc. existed before computers, probably in much the same way as they do today.

Lots of authentic documents are illegitimate.

You want the government to be more effective and efficient at tracking people?

They already:

* have access to your internet usage, search history, and phone records

* track our location through cellphones

* have surveillance cameras everywhere, in case you didn't bring your phone

* track where your cars is through a vast network of ANPRs

* fly drones/planes over cities doing aerial surveillance

And you think that tracking the number of H1B visa holders is too much?

The roadblock as always is bringing all that info together. Few places have access to all that information and a way to synthesize it together.

well if they claim the H1b program is abused, you bet I'd want them to have real data to report that