How fiction affects reality is about how it meshes with your internal templates for how the real world works.
Ratings are based on a rough estimate of when most people will have those templates form. For instance, there’s a standard for children’s media which states that you’re not supposed to include imitable violence more severe than an open-handed slap, because kids are just learning the overrides for the monkey-brain “if someone makes us angry, we hit them to send a message” drive. You can’t make a show for preschoolers that shows how to throw a punch, because they might very well just start punching people.
But you can show your average teenager as much punching as you want, and unless their parents REALLY fucked up, they won’t take it to mean “this is how you solve ANY problem, from a threat to your life, to someone looking at you funny.” When you can show the use of realistic guns to a person without them deciding that shooting people is a good idea depends on a lot of personal and cultural factors, but as a standard we can settle on people tend to agree that, as long as it doesn’t settle into reinforcing stereotypes as a possible invocation of “things that are okay only to defend your own life” or blatant war propaganda or similar exceptions, most adults can see all the violence they want - yes, even glorified violence - without turning into a violent menace themselves.
If you have it impressed upon you your whole life that killing people is bad - as you will, unless you have the worst kind of parents imaginable - you can watch your favorite action star kill tons of dudes, or play games that are just excuse plots for killing tons of dudes, or read about a million and a half creative ways to get away with killing tons of dudes, and you’re still not going to run out and kill tons of dudes or even think it might be okay to kill tons of dudes. This is because your mental template for how the world works strongly emphasizes “death = tragic; killing people = hurtful and bad”. Again, it might fuck with your head if the explanation for why killing tons of dudes is justified in the context of this piece of media aligns with common stereotypes of real people, or your own preexisting biases - this is how propaganda works - but even in THOSE cases a lot more factors have to align to get someone to the full extreme end and think “yes, killing tons of dudes irl is the answer to all my problems!”
It’s where people have weaker templates that’s really a problem. For example, most Americans have no idea that Cairo in the modern day like this:
…because they’ve been inundated with media that portrays Egypt as looking homogeneously like this:
And - and this is the important part - they have had little to no experience to tell them otherwise.
Now, I’m assuming the majority of the people reading this post don’t live in Cairo - if you do, take this shoutout! - and if you are in that majority that doesn’t, imagine if someone tried to pass something like this off as your own hometown. Obviously, you’ll call bullshit! You’ve seen that place and it’s nothing like that!
But if it’s a place you don’t know anything about beyond the fact that it exists and has these famous landmarks for these famous historical reasons, then anyone can…pretty much just say whatever they want from that baseline, no matter how absurd, and you will probably accept it as, if not a fact, at least a believable fictionalization with some basis in reality. At most, maybe you’ll go
This is how media creates and perpetuates stereotypes - by getting in where you don’t know better and forming your mental template. It can even work if you do have real-life counterexamples, when those real-life counterexamples are uncommon enough or you don’t spend enough time with them - if you know maybe 5 members of a minority group and none of them act like the 500 stereotyped examples you see on TV, you’re likely to end up thinking “okay, there are exceptions to the rule”, rather than “the rule is bullshit”.
This is why “honest, varied representation matters” and “not all fiction is 1:1 monkey-see-monkey-do propaganda and it’s really dickish to assume the worst of someone just because they like one (1) game that you see unfortunate implications in or something” are both statements that can and should coexist.