First of all, welcome to the community! 
I’m Canadian, but we’re basically a frigid growth on America’s back, so there are a lot of cultural similarities.
Do USA teens really act like the characters of the stories?
Short answer is no, long answer is that that stereotype doesn’t come out of nowhere.
Hollywood and drama has kind of become a parody of itself, imo. A lot of these stories (like on Episode) are all based off of cliches of each other, so it becomes like a game of Telephone, where the end product is a warped version of the source material.
And Ray above me definitely has a point; America is probably among the top 20 countries in the world when it comes to general comfort, safety, and wealth of the general population. This causes them to have fewer problems, and their biggest problem is likely something that their counterpart from, say, Yemen, would find trivial. I don’t think American teens are necessarily more comfortable than their counterparts in Australia, Canada, or the UK, etcetera. The reason that people around the world tend to equate “American teens” with “Western teens” is likely because America has more people than Canada, Australia, the UK, France, Germany, Belgium, the Netherlands, Finland, Denmark, Sweden, and Iceland combined. America’s cultural impact is therefore proportional to its population. They make more movies, write more books, make more Episode stories than, again, all of those countries I just mentioned, so their culture tends to drown out the media made from smaller wealthy countries.
I could type at length about America’s cultural impact, their awareness of their own cultural impact, and how that awareness feeds back into an isolationist, near-nationalistic view of themselves, but not only am I some weirdo with an emoji profile pic who doesn’t have an anthropology degree, but that’s not even the topic of this discussion, so I’ll continue.
I graduated high school in 2013, coming out of there with no friends, so I can’t claim to say that even the information about my own school is correct, because I was so far out of the social loop. But I did observe a few superficial social dynamics.
Before I address the specific questions, I’ll say that the idea of “popularity” and “cliques” existed, but not in the movie kind of sense. There were groups, but many groups were harder to classify, and most were relatively cool with each other. In the lunch room, you’d see patterns, people generally sitting at the same table with the same friends, but the kids with good social skills would talk to each other if their close friends weren’t available. The lines between cliques were blurrier than in the movies. The oddball kids, the ‘geeks’ so to speak, were generally a little more cliquey than the kids with better social skills (ie. the ‘popular’ kids), because the ‘popular’ kids would talk to whoever made good conversation when they were bored.
And maybe it’s a millennial thing, but especially in grade 11-12 (ie. the last two grades of high school before graduation), it definitely wasn’t ‘uncool’ to be thinking of your future and university opportunities. There were plenty of ‘popular’ kids who were concerned about their marks in math and getting enough extracurriculars to be considered for their choice universities.
Definitely not. Next question. 
Kind of? Generally, the sporty guys fell into the ‘good social skills’ category as mentioned, so they were good to chat with anyone.
There was definitely one clique of geeks (or possibly two. I was part of one of them briefly. I never joined the other because it had this girl who hated me.) They weren’t bullied relentlessly or anything, but often didn’t fit into the ‘good social skills’ category. Many of them would rather read or play on their phone rather than chat with their classmates during breaks anyway. I feel like for the most part, the ‘good social skills’ category were too busy with their own lives to bully that much. Some people occasionally, briefly, made fun of the quirkier members of the geek group, but it was more of jokes rather than incessant harassment.
I definitely wouldn’t say that I wasn’t bullied in high school, but it was less than middle school, and a lot less than a character like me would be bullied in a cliche Episode story. Silent girl with frizzy brown hair, glasses, acne, and weird scars on her two front teeth who barely talks to anyone and can’t make eye contact? Classic target for stereotypical bullies. But 90% of the bullying that I faced was some odd “proxy bullying,” because there was another girl with glasses, acne, and frizzy brown hair who acted like a weirdo, and people associated me with her. (We occasionally frequented similar circles, but we were never actually friends). Besides that, I was content to fade into the background, and people were content to let me.
Relationships like dating? I paid even less attention to that lol. Especially in the later grades of high school, I feel like no one really made a big deal of who was dating who. There were probably the occasional tough breakups and such, but I don’t think it made much of a splash in any sort of “gossip mill.” Then again, the only times I heard gossip was when I was eavesdropping lmao.
If you have any further questions, I’d be happy to answer them at length haha. 
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