the OP's list of Korean manners make the Koreans look like idiots or barbarians lol
on defense for the koreans:
unlike the many myth that the waygooks have,
it is also rude to stare at people, albeit us getting stares here (thats because we are foreigners)
let me give you an example.
Have you heard of the expression "mol ggoraba?" from the students?
It means "why the hell are you staring at me". When you see kids fighting on something, they would typically say this to intimidate or to agitate the other. Anyway, staring is considered impolite here as well.
Forreals haha...that's the first impression I got too when I read the first few lines.
But here's a few in defense of Koreans:
-Don't hug people you're not close with (you will spook most Koreans)
-Don't give a hard-firm-military-handshake (that's very disrespectful and is unnecessary)
-Take your god damn shoes off at the front door when you enter some one's house. Or at restaurants that requires them off.
-Don't like fish? Don't eat meat? Oh you're a vegetarian! (will make the best out of it anyway by picking at the plentiful veggie side dishes) Vegetarians don't have a special status here

U.S.
-You assume everyone is AMERICAN! Don't ask them what country they're from? (As an Asian-American born and raised in the states, most white folks still ask me this...never cease to amaze me.

)
-Turn off your phone when you're on a date or in a meeting. Do not text or answer any calls.
-It's okay to get pissed and throw tantrums at the customer service...because "The customer is always RIGHT!"
-Horrible customer service.
-People get easily pissed if their foods aren't made right "Excuse me! I want medium rare....overeasy... not fully COOKED"...or some obese folk ordered diet coke and got regular coke.

-Group outings and eating...Americans always worry about how the bill is going to be divided among each other and who should pay the bigger "tip".
Korea:
-Oh you speak english. "Where are you from???"
-Customer service is almost too good that it comes down to it being too overbearing-annoying with a store staff following you all over the store.
-You cook your own DAMN food on a grill! So fun!

-There's no tipping after you eat! And the bill is usually covered by an individual person with no hassle (most Koreans see the western way of dealing with this issue as being selfish individuals)

*Brings back high school memory working at a fast food and theater lol