Not a yank, but according to my research historically some states (and even some cities) had dissimilar voltages, amperages, and plugs, and even a choice of alternating vs nonalternating current. Sort of like how the poms have 100V instead of our 240V but with only a few kilometres of distance involved, dependant on power company.
Knowing what the different States are and different cities (for the title text) is pretty important. As someone who is from outside the United States, I wouldn't've been surprised if "Pennsylvania Wiring" was really a standard of wiring.
I think the joke would have been better and more understandable if it had used different corporate names rather than states. But, of course, that might have been legally problematic.
IMO the joke is more "timeless" because it uses state names instead of company names.
Imagine if instead it mentioned Xerox computers, DEC terminals*, IPX, and Ethernet hubs. We'd say "wow that comic didn't age well". Even something as recent as "EVGA GPU" will go down in history books instead of commonplace.
*Yes, I am aware that the VT100 terminal spec is from DEC. But they don't make DEC terminals anymore
10 years down the road, we don't know what tech will look like. But there is a high likelihood that the state of Pennsylvania will still exist and hold relevance.