Woodlands is the busiest immigration checkpoint on the planet and it's only 1 of 2 crossings. It's fairly seamless for regulars apart from Friday afternoons when it gets clogged up by escaping Singaporeans keen for the weekend and the quality/value offered by their poorer neighbour.

https://en.wikipedia.org/wiki/Woodlands_Checkpoint

There's people who live in Tijuana, Mexico and work in San Diego, California and that's way worse than Canada/USA in terms of time and hassle. Not something I'd want to do, but then I wouldn't want to live in Connecticut and work in NYC, which many people do either.

> Must be a fully automated border or something?

Oddly enough, not until very very recently (~2024). Traffic jams of several hours are still quite normal for vehicular traffic, and it is the busiest crossing on the entire planet, with up to half a million crossings a day.

Where are you located? Lots of such crossings used to happen, anyway, many years ago via Nexus or similar. Get the pass, just drive right on through over the bridge at Windsor/Detroit. Also similar things in Vancouver, I believe.

I had an unplanned short stop in Singapore in December after missing a connecting flight. I just filled in an arrival form online (no Visa), went through the electronic gates, an officer glanced at me and let me through without a word. Whole process took about ten minutes, and it would have been quicker if I’d filed the paperwork beforehand.

I don't know about the USA, but such an arrangement is extremely common in Europe thanks to the Schengen area.

US borders are awful. I guess you get away with it because the USA is so large that most people rarely leave, so rarely have to experience it.

There are actually a fair number of folks that commute from Canada to the US for work. They will generally have TN Visas, it is certainly not "unthinkable" - it really does happen, although I will confess that the only folks I have ever met that did it were not recommending it to anyone else!