North/WMG

The Reason for the Ethnic Stereotyping
... is all the families in North are the horrid ethnic stereotypes that they are is because North is imagining the whole thing, and in his head, that's how people act.

That's right, in his head, North's either a) A child whose parents have reinforced negative stereotyping, b) a racist little bastard or C) a kid who needs to turn off the TV and open an encyclopedia.

It's all in his head, including his Gary Stu-ness.
He's not a model student, athlete, actor, or anything like that. He's not even half as smart as he thinks he is. He's not much of anything... beyond being a racist, self-absorbed little Jerkass who overreacts to anything that doesn't involve him getting exactly what HE wants, WHEN he wants it. The whole thing is All Just a Dream he has to justify his horrible mindset to himself: "My parents may not give me everything I want, but at least I'm not (Fill-In-The-Blank), right?"

Anxiety Attack has medical causes
The dyspneatic anxiety attack at the beginning is not a normal child's reaction to parents fighting, instead it may be indicative of a serious bacterial infection. More specifically, he may have a serious bacterial UTI and approaches renal failure, causing metabolic acidosis (of which shortness of breath is a symptom). The fact that he falls asleep later on the couch in the middle of a conversation furthers this hypothesis: North is actually sick, his hallucinatory, incoherent dream of abandoning his parents is an expression of his subconscious realization that his parents didn't notice how sick he is. In his attempts to be the perfect overachieving son, he stopped telling them of his medical issues - UT Is can be quite embarrassing to describe.

The Guardian Angel is trying to kill North, and is Freddy Kreuger's good-guy brother.
That racist little brat needed to be struck down by God. Bruce Willis was chosen to assassinate him, and put him into a purgatory dream where his friend tried to kill him. In an Elm Street twist, anything that happens to him in the dream will become real. (un)Luckily, North wakes up. By driving him home, Willis gets an ample opportunity to strike again when he falls asleep in a few minutes.

Bruce Willis's character is an Inception agent.
He is performing Inception on North to convince him to remain with his parents rather than leaving. The nonsense and stereotyping is all exaggerated in order to convince him. Occasionally he will appear himself just to nudge things a bit more they way he wants them. He's not all that great at it, because he leaves a lot of holes in the logic, such as justifying North's original parents, but that's alright because North's just a kid anyway, so he doesn't notice. The Inception works and North goes back home.

North doesn't actually view people the way they're shown.
It's a dream. Crazy things happen in a dream, we can't control them unless we try, and sometimes even that goes horribly wrong. Who's to say the stereotypes aren't just crazy things his brain made for this particular dream?