I had the same type of experience heading south on I-87 in New York.
Homeland Security and NY State Troopers had set up a roadblock on the interstate, and marked it as if it was a lane reduction for construction.
Once we got to the actually roadblock, they were asking for ID from everyone coming through. The car in front of us had a black family in it, and they had a Quebec plate on their minivan. The car was loaded up like they were going on a roadtrip or something. Somehow, the Officers speaking to them decided that these people were suspicious-looking, and proceeded to ask the family to get out of their van, remove their stuff and sent a sniffer dog through the van. Their young children looked pretty scared by the whole thing (it didn't seem like the kids understood much english - so they looked pretty confused by what was happening).
Once this family was pulled to the side and they and their belongings were out of the way, the officers waived us forward. I suppose Americans were able to show a driver's licence or something, but since I'm Canadian, and an Ontario plate on my car, they wanted to see a passport. Both of our passports were in the trunk, and we nervously told the officers that we didn't have them handy. He just looked at us, shrugged, and waived us through. Behind us, that family from Quebec was still behind harassed as we drove away.
For us, it was just a delay, but it was hard to watch how they treated the family in the minivan. Getting stopped at a random checkpoint by Troopers, with Homeland Security officers behind them with machine guns and Hummers really drove home how much the US has changed.