Colder climates would be harder for the bugs to survive. Terrain, flora, and fauna would produce variations in this too. Just high school biology 101 kind of thought.
People often confuse luck with virtue.
I live in Florida and spend most of my time crawling around where wild animals are... I’ve seen nasty bugs of all kinds and lots of parasitic critters... but I have yet to see a bedbug. Not even in my birds’ nest boxes outside. Worst thing in those are seed beetles, which are annoying to look at, but they don’t bite and the larvae make good chicken and fish food.
Now, I have a relative who is a stewardess who says the darn things are everywhere the airline workers go as some of the stewards and stewardesses are constantly transporting them around. When she travels she won’t even bring luggage or clothes into the house... every stitch of clothes goes into the laundry while the luggage gets stuffed in giant garbage bags and gets fumigated.