I live about the same distance from Germany as I do from Romania and I wasn't insulted in the slightest by that detail in the movie. I figured that because of what's been going on in the MCU, Loki in NY and Stuttgart, Ultron in Eastern Europe and Korea, Dark Elves in London, evil wizards in Hong Kong (though I forget if the city was repaired by Strange's use of the Time Stone), the human governments would be more open to a higher degree of cooperation. Germany, Romania and the US are all Western countries, so they'd already have connected institutions that could quickly be turned into a unified command structure.
Well fair enough. Guess there are some people who are less insulted by that bit them.
And there already is NATO.