This is a 2-month ban on a VERY limited type of occupations or types of immigration. For people already in the country etc., it has no effect. It’s mostly posturing toward his political base - I’m sure you can understand how that works in terms of political communication.
But most importantly 1° there’s an election in November 2020 2° there’ll be an election in November 2024. But also parliamentary elections in 2020 and 2022. In other words… things can change A LOT.
But if that worries you, look at approval ratings, or Biden v. Trump polls in key (“swing”) States such as Wisconsin, Michigan, Pennsylvania. (Yesterday, as a joke, someone said, ironically, “and now DT is a polling error away from losing Texas!” It’s a joke because even though the numbers are real, we’re six months away from the election and six months is a VERY long time in US politics. Anything could happen. So… for us… 4 years down the road… it’s likely whatever is passed now will have been undone and something else will have been passed. In other words the joke DOES NOT mean “DT may be losing Texas” although some people may wrongly interpret it as such, but rather “things are really, really fluid right now and remember we’re a long time away from the election and things are likely to change 20 times between now and then”. Yes, 6 months really is a VERY LONG time in US politics. 
I know it’s hard to wrap your mind around this if you’ve lived in a dictatorship where the only constant is the dictator’s arbitrary whims, but those are US constants: elections do take place and do change things.
A rhetorical decision followed by a much-diminished act that only applies for 2 months is NOT going to make policy for years and years to come.)
BTW, your son will feel welcome on college campuses. Americans, especially American students, will be VERY unlikely to treat him badly.
Some might but they’ll be a minority (like 1 in 5,000 minority); my guess is that your son is used to being treated unfairly at times and has met jerks before.
Mostly, he’ll find that most Americans he’ll encouter will be friendly, sometimes interested in his perspective or past experiences, and eager to share their values or perspectives with him.
You could BTW ask each college you’re considering 1° whether the current ban will affect their international students in any way 2° whether the college organizes international students “friendship families” with whom they can have dinner or play a game from time to time.