All you need to know is Mordin is awesome :D (though I might be bias, maybe.)

Heee yes this would be very interesting! I admit to knowing very little about Hetalia. The one question I do have is do they know they're countries? 8|9

Also, this is where it gets kinda complicated? Because Captain America comics do exist in the Marvel universe and Steve knows that he's a comic book. So he won't believe that he's a fictional character anyway. Likely he will just assume he's read those and seen a movie or something |D