The biggest is Neil and MC's poverty, it's just not believable. I'm not saying that there's no poverty in the US, there's way too much, but poverty is relative to the overall wealth of a society. In the US families that have lived on government aid all their lives have color tv's, smartphones, microwaves and etc. Outside of the major cities most Americans own cars, often more than one per family. And the overwhelming majority have air conditioning, in fact I can't remember the last time I saw a car or truck without AC, unless it was a vintage. Almost all houses and apartments have AC.
Neil's income is way off, a construction worker, especially one with 19+ years on the job, is earning a very good income.
Given this we see MC saying he's never been in a car with AC. There was a similar scene where he commented on seeing color tv. Then there's the car's. Where are they? Even the students from relatively affluent families don't have cars. In fact cars, and parking are a major and growing problems for college's, building and operating parking garages have become significant line items in their budgets.