Most all replacement rotors are now made in Mexico or China with the latest shift toward China.
A couple of years ago, it was my mission to find an American made rotor for my Dodge Dakota. I went to several stores and I finally found a rotor in a small mom-and-pop store that made in Canada. The reason that it was made in North American was because it had been sitting on the shelf for about 10 years. I bought it, but the for the next rotor I just accepted the cheapest one I could find, one that was made in China.
However, about a week ago I was shopping for two front rotors for my 2WD Aerostar. I priced them at RockAuto, but with shipping figured in, they were cheaper at O'Reillys. I purchased two of them. One rotor was about a year old and was made in China. The other rotor was just a couple of months old and it was marked that it was made in USA. I initially was happy about that, but I suspect they just installed the wheel studs in USA or maybe just installed it in the plastic bag so they could qualify it being an American-made part.
To the OP, remember that AC Delco is just a parts relabeler and won't be the same parts that GM now uses on the assembly line.