I am well aware that making this post will probably make me sound like a jerk but I just can't help myself.
This problem is very very cultural and while you don't consider some things as fake someone from from the outside can sense them as very fake. Number one reason is that America is very capitalism oriented society and therefore from young age you absorb this culture of succes and try to imitate it (at least most do). In American way of life there is actually very little certainties and therefore you constantly have to be on the offense of some kind, what some other nations see as "unatural". For example America and similar countries made an entire science of how to address people down to the last detail, what to someone who is not born in a system that prizes such behaviour can seem as fake. Since I am ambitious I got into situations where I have to do things in a more western way and in general I came across as too blunt (just as others from my part of the word). What is because we don't play so many image games with others, not even subconsciously. Due to the historical reasons we developed pretty direct and straight forward language whose task is to say maximum number of precise facts in the smallest amount of time possible. Therefore in some cultures/situations passing on the facts is much more important than tone of voice, details cloths and similar to that. Therefore since USA recently didn't have any large war zones on its territory there was never a need to push very direct conversation styles in society. Instead conversation could have been more "image oriented" since there wasn't immediate threats.
Another problem is that America is constantly pushing this "number one" thing even if in many many categories it simply isn't number one. USA was number one in pretty much everything a few decades ago but now this is mostly old fame. What makes Americans look like one of those people who show off in many ways but they just don't have something that would cover this image. I mean there would be no real problem that USA is not pushing this image at all cost, what makes Americans look silly. Especially since a number of first world countries have overgrow USA in many aspects. For example number one economy per GDP is EU, and if the union will continue to spread the difference will probably even grow. Also many countries outperform USA in very important areas such as freedom of speech, quality of life, quality of food and violence index. These days on international knowledge tournaments for highschool children USA usually takes something like 15th or 25th place, what turns the whole No 1 thing into a unfunny joke. (feel free to google about the issue)
Extra but not less important thing is the American culture that is exported around the world. Obvious example would be the American invention known as "fast food": looks nice, often tastes pretty good, it is constantly advertised unlike many other types of food, it is realtively cheap ... but it can kill pretty easily if you are not careful. Same is with TV which has countless shows that scream either dumb or fake. Does anyone remembers Jerry Springer show ? If that was not fake then I don't know what fake means. Pretty similar can be said for Oprah show or Dr. Oz which are basically just well packed advertisement for various products, people and events ... and don't even get me started on Big Brother and similar stuff. The truth is that if there are so many such shows that means that they are part of the culture and can't be considered as something else entirely. Another thing that comes as fake is censorship of bad words on TV with "BEEP,BEEP" sounds. I know he said "Fuck you" , you know he said "fuck you" so I see no real reason not to hear that "fuck you". I mean if this is so bad then cut it out from the show entirely, but no someone has to be a whore and a saint at the same time. I mean USA is possibly the only country where you can be drafted but at the same time it is illegal for you too drink beer. Same is with prison population, USA is land of the free but it has largest prison population in absolute values and compared to its own population size.
What step by step leads to the obvious candidate of American fakeness "Politics". American politics is completely full of people who have no real opinion on their own, it all depends on what are interest of the people who pay for their campaigns. Even when you look at those people in politics they in general don't even seem as this is trully their real opinion. Even the media are like "Wow, this will hurt their image very much. We here in the studio are not sure that he will be able to recover from this blow in time". While at the same time no one really care what was actually said or are these just parts of some larger trends, people interested in politics simply don't seem to be interested in botom line since it is all about winning. Which is done throught image and entertaining public, having a better joke than healthcare plan can make you electable in USA, what says trully a lot about the nation, especially if that same nation is pushing itself as number one and role model. What in the end leads to scenario that someone like Trump becomes relavant simply because he is pretty genuine in comparison with other ... but it doesn't have many other strenghts. What clearly shows that the society has a problem in genuinity related issues.
This thread asks why Americans seem as fake and I just wanted to adress why many none Americans make this correlation. I could have been more brutal in this post but my intention really isn't to insult anyone. If you live inside the system you probably don't notice most of this, but when you observe from far far away things can look very differently.