I am by no means an expert, but as far as I understand NO2 pollution is mainly generated by internal compustion engines (especially diesel?), so I don't understand why there would be a causal link to A/C use. I can imagine various reasons for there to be a correlation without direct causation, in particular because the atmospheric chemistry of NOx [1], though to be honest I don't really see the correlation you mention just from the visualizations.

The data are (or will be) available in the sources mentioned here [2], if anyone wants to analyze them (I think, I haven't actually tried to access them). I don't know where you would get geospatial data on A/C use to compare with though.

[1] https://en.wikipedia.org/wiki/NOx [2] https://tempo.si.edu/data.html