It’s both. The glasses in Hetalia often have multiple functions. 

Austria wears them to avoid looking plain + they represent his musical something. 

Source: Hetarchive, Notes and Etc.

Estonia needs his glasses because he has poor vision + the glasses have a tendency to summon “unusual fellows” (i.e., the nyos, aph God, and the mochis). 

Source: Hetarchive, (Bamboo Thicket, eng trans., Feb 26th, 2011)

America’s glasses represent Texas + they also allow him to become a super hero when he takes them off (I’m not kidding). 

Source: Hetarchive, Comic Diary 2 + Hetarchive (Bamboo Thicket, Feb 25, 2013).

Uhhh…. off the top of my head…

England drinks too much and consumes too much sweets. America eats too much fast food, partakes in extreme diets, and workouts out to the extreme. Spain gets violent when he’s drunk. China once got addicted to video games. 

I cannot chill because Uni and its fuckery but your kind wishes made me feel better 🙂

Oh, I know and thank you :D! Haha…hardly necessary to give life updates when I post 5-6 days a week.