Cracking up at a friend’s joke while exposing your pearly whites is perfectly fine in the United States. Not in Japan, though.
While in most countries abroad, tipping is not expected but appreciated, in South Korea and Japan, this gesture is considered bad etiquette and an insult.
Asking for a condiment is considered an insult to the cook in these countries, as it implies you find the food bland.
In Japan, France, or the Middle East, however, refrain from blowing your nose in public, as these countries consider this gesture incredibly rude and repulsive.