Before coming to the U.S., some people told me that Americans are very nice, warm and friendly, while others said that the western culture and philosophy is about egoism, highly individualism which means little emotional bonds among people, in other words, Americans are selfish and cold. Those were what I have been told before.
(Neither is true~~~)
After living here for a while, based my observation and feelings, Americans are indeed nicer in some aspects, such as TALKING. It is way too easy to get complimentary words from my dear American friends. Foreign new comers are sure to be flattered all the time all the time, but as time goes by, they will figure out it and become the ones who output nice words.
So newcomers, please take a conservative attitude when people here say you are amazing, great or something is wonderful, perfect. Most of times, it is just a habit of saying like that, the truth is you are still who you are, your worries are still out there, just enjoy the compliment for a second and then get back to real life.
Once one of my classmates tried to borrow a handcream from others, another classmate said she might have one and looked for it in her purse, murmuring it was always messy in the purse. The girl borrowing handcream said wow your purse is nice!! I was about to faint. Yes, her purse is not shoddy, but sometimes just can not take good words too seriously.
Americans always have ideas about saying something not very respectable in a sweet way. For example, paying for a mistress is called “mutual beneficial relationship” which sounds really nice. True, both sides enjoy the benefits. Also, the rich old man and beautiful young women get the sweet name which are sugar daddy and sugar baby rather than cruel names, like 包养 二奶（you may Google them) in China.
In comparison, Chinese are educated to save complimentary words for the moments when things are really outstanding and exceptional and in the occasions where they are necessary. See? there are several strings pulling Chinese back from saying nice words. But not saying complimentary stuff does not means they do not like you or things you do, they are just admiring you in hearts.
Personally I think being nice or not has more to do with who specific person is than the territory. Nice people and freak ones spread out every corner of the world, and sometimes a nice person could be unfriendly in some certain circumstances. People just have different ways to show how they love or dislike this world and people around them.