Oh noooooo! I could see Romano freaking out at himself as well because WHAT IS HE DOING?!?! but he can't stop himself so as he sees Germany getting frustrated with him and disappointed, Romano just starts eating as much of the food as he can. Like, how else can he show that what's coming OUT of his mouth is a load of defensive crap except by putting loads of what he's badmouthing in there?

Germany: ...You don't have to eat it if you don't like it.
Romano: No, shut up! I'm gonna!

It's like that meme where person A makes person B a friendship bracelet and person B is like wtf???? but then refuses to ever take it off.