And DUI checks, and 'random' stops where the officer in question didn't like the cut of your jib, smelled pot in the car, and would love to know where you're going.
America's a big place, there's a very wide range of things that law enforcement do in it.
Only in states that permit CBP to operate inland checkpoints. California banned the practice a few decades ago, you can see where the CBP used to operate checkpoints between San Diego and Los Angeles as you drive north along the freeway.
Yes, but very limited. They are only allowed to ask "are you a US citizen", and walk a dog around the car. I've never had one take more than 60 seconds in either AZ or CA.
I'm a tall middle aged middle class white man and I had no issue with any police check in my life either.
I think there are demographics that have different experiences than mine, especially when there's a dog involved (who can provide any excuse necessary:)
I don't believe police at checkpoints in Canada are walking dogs around the car or asking whether we're citizens or not, it's just a matter of whether or not someone's had drinks, I'm fine with it
In Australia I've been stopped many dozens of times for a "random breath test" where they stop every car and make you blow into the device to check blood alcohol.
As a Canadian, in Australia, I was surprised by the random breath test. That is not allowed at check stops in Canada unless there is another reason to suspect you have been drinking (smell of alcohol, slurring words, that sort of thing).
America's a big place, there's a very wide range of things that law enforcement do in it.