Angry Couch Potatoes
I saw that list and that's immediately the first thing that came to mind. They all eat a lot of potatoes.
Potatoes are really, really bland. They're not even technically a vegetable, they're just a starch. Filler. Something our obese populations don't really need right now.
It takes so much to make potatoes tasty - spices, cheese, meat, whatever you can add to make them better. At the very least butter and salt.
I used to joke that the reason the English were such colonizing bastards is because their food tastes so awful they raided the rest of the world for better flavors. I only feel marginally bad for making that joke. Partly because I'm only half joking when I say it.
Also their language is gruff. When English speakers say "Pardon my French" the words they're about to use are actually more often than not of Germanic origin. They're dropping their fluffy, Latin roots for some potato-dirt verbage.
I could add beer to this mix, but so many civilizations rely on beer and other fermented beverages that it doesn't seem very discerning to bring it up. Plus you didn't include Belgium on this list, and as far as I've read everyone in the northern Germanic areas took their best beer-making tips from them (that statement may start a fight now - have at it, I prefer vodka anyway).
There's also the fact that their descendants remain oddly dairy dependant, when in reality the majority of humanity should be lactose intolerant - you don't need milk after you're done breastfeeding for most mammals. Yet while roughly 65% of the world's population is naturally lactose intolerant, only roughly 25% of these Germanic populations are. Although if you're wondering that does not mean the rest of the world doesn't have a rich history of dairy production; unfortunately it does mean that you need to ignore these people if they try to tell you how to do dairy, because they don't need the microbes you do to break down lactic acid.
If we're hoping to find some sort of common, gosh-this-racial-group-just-produced-some-right-bastards genetic or cultural underpin that explains what the hell is wrong with them (actually I should say us as I'm a mutt of this genetic variant myself), I've got nada.
Unless maybe just centuries of stuffing yourself with starch, alcohol, and lactic acid makes for creating a cultural group of angry couch potatoes?
Hmm, yup gonna go with that.
*post title set*