Can a cop pull you over walking home asking why you are out so late?

I was going back home from my office, around 3 or 4 am. Huge project to hand in, I just kept on going until I had it finished and polished, and when I finally managed to finish I drove back and started looking for a parking spot.

Uhm, just as a note: Europe, not US.

That's when the policemen spotted me: I was so tired I was unable to park where I found a spot, and just drove to the next one I found. When I left my car, they pulled me over and asked me a bunch of questions (the usual ones, like where I was going, where I was earlier, etc).

What are some signs that a therapist may have poor boundaries with their clients?

Sure they can. It happened to me a few years ago.

I was polite throughout the whole interaction, there wasn't much they could do. They weren't nice until it was clear I was just tired and not DUI, but that makes some sense.

I told them I was in the office. They asked if I'd been drinking. I told them I was just too tired to park properly and wanted to go to bed. They kept asking dumb questions about my job (I was so tired I’m pretty sure I was really confusing), so they gave me a breathalyzer test, and then let me go once they understood they were just bothering a poor person working too many hours.

What would happen if the US government told the British government in no uncertain terms all RAF bases with USAF personnel now must follow the Constitution and us law, and if the UK tried to defy this, the US military would directly attack the UK?