Brief disclaimer to get it out of the way: My OTP is Romerica, and I ship Gerita a lot. I’m probably not the best person to write this meta, but I’m not opposed to Germano and have thought about how it could work within the canon universe, so I’m going to give it a try.
If you take a very shallow view of Germany and Romano’s canon relationship, pairing them together doesn’t make much sense. Romano is hostile towards Germany in a way that goes beyond his typical tsundere attitude, and Germany is closer to Veneziano (and there’s a whole arc about him having romantic feelings for Veneziano in the Buon San Valentino strips). But the reality is more complicated than that. Romano is most hostile to Germany in the earliest written WWII strips, and he’s clearly softened to him in modern times. In chapters 357-360 of Heta World Stars, Romano rides in Germany’s car and admits to thinking it’s cool. He’s even comfortable enough around Germany to fall asleep during the car ride. Furthermore, Veneziano’s reaction during Buon San Valentino after Germany shows him the tomato ring suggests that Germany’s feelings are one-sided. Veneziano says “I’m sorry” repeatedly and says “I appreciate your feelings, but—” These aren’t normal reactions for someone who returns romantic feelings, even if you take into account Veneziano’s confusion throughout their “date.”
Here’s how Germano could develop in canon verse: After Buon San Valentino, Veneziano sits Germany down and makes it clear he sees him as just a friend. Germany is heartbroken of course, but he stays friends with Veneziano (and thus remains in Romano’s social orbit). At some point, Veneziano might date someone else, and Germany tries his best to be happy for them because he values his friendship with Veneziano and possibly whoever he is dating if it’s someone like Japan that Germany is also close to. Gradually, Germany’s feelings for Veneziano fade, and after a while he is able to be his friend without lingering sadness or jealousy.
Meanwhile, Romano’s distrust and hostility towards Germany begin to fade as he spends more time around him. Post WWII, he starts to see that Germany isn’t that bad and that the assumptions he may have had about him based on WWII or Germania (since he was scared of a German soldier as a child, which suggests WWII wasn’t the only issue) aren’t true. Instead of hatred, there’s grudging respect, which Germany reciprocates. From grudging respect could come genuine friendship, and then, after a long time, love. By that point, Germany would be over Veneziano and therefore able to consider Romano in a romantic light. If Romano started liking Germany while he was still hung up on Veneziano, it could be really unhealthy for him given his insecurity issues surrounding his little brother. Fortunately, Romano is really stubborn, so by the time he admits to himself that he likes Germany that way, Germany would be in a position to at least potentially reciprocate.
The things that initially put people off of shipping Germano (Romano’s hostility and Germany’s feelings for Veneziano) are actually what make them interesting as a slow burn ship. It’s different from other slow burns that could happen with mutual pining and miscommunication tropes. To even get to the place where they could see each other romantically, both Germany and Romano have to go through a lot of character and relationship development first.
