I have both versions of the Irwins. I have to say there was no change in quality on that particular tool. My US ones are all black plastic and the china ones have some blue plastic.
They are good tools. They are quick, grip well, and a good weight. They do flex a bit, but move the piece less than the screw-down type of bar clamps.
For the BEST clamps, get Bessey parallel bar clamps.