I call this BS. We had one or two days the summer where the temps were in the low to mid 90’s. In Rochester, NY, it was 100 degrees on June 21, 1953. I was 5 years old. On July 10, 1936, in Rochester, the temperature reached 102 degrees. There’s been temps in the high 90’s in Rochester, since they first started keeping temp records.
A ridge of high pressure has been parked over the south central and southwest since late June with record highs in Texas, New Mexico and Arizona. The location may be dependent on global wind patterns (as you say, not every place like NY was affected), but I’d put the blame for the degree of heat on the water vapor in the atmosphere, as H2O vapor has much more of an impact as a greenhouse gas than does carbon dioxide.