Sometimes, it looks like that other nations forget that Germany is chronologically young. And it looks like he still has something to learn about being a nation. Like, Italy won’t die just because the seats of a car sends him flying into the air.

I agree, that scene
where Italy’s catapulted into the air by a faulty car seat does reveal a bit of
naivety on Germany’s part.

On the other hand, Germany’s
young age is mentioned several times in the manga. There’s also the fact that the scene above took place during WW2. Germany would have learned a lot more since then.