I think the Austrian Flair should be "Fritzl-Kind", "Consensual Non-Consensual Anschluß" or "Germanized Slovenian".

Spain should be "Discount México" or "Catalan bussy enjoyer"

Dutch... Dutch is enough of an insult already.

Germany could be "Greater Bavarian", "it was Versailles fault" or "It did happen and we enjoyed it"

France could be "Arab Republic of France", "Snail stuck in Urethra" and "Algeria deserved it"

UK would be fun to call them "Americanized Franco-German", "Fish with no chips", "IRA did nothing wrong", "Chief shagger of the sheep"

Denmark: "Southern Swede", "Dogs of Greenland"

Switzerland: "Women's rights are optional", "World War champion", "Greater Albania"

Belgium: "Bosnia but worse and gay", "French speaking Dutch", "We exist, for real"

Luxemburg: "Wannabe Switzerland", "Lichtenstein but somehow worse", "Divorcee"

Norway: "Dad died on an oil rig"

Italy: "Ariete tank is good, I swear!", "Southern Tyrol is supreme Italy", "Pompeii deserved it", "Venice->future victim of drowning", "What is sexual harassment?"

I can't think of any other dumb shit for now but feel free to add more