Other than some of the issues brought up in the comments (correlation/causation):
- Trump hasn't been president for more than a year, so it would be hard to prove anything absolutely at this point. We can look at the trend over time to see if that has changed, but less than one year?
- This article indicates that 40% of unis have seen reduced foreign enrollment and the article attempts to prove this is related to the political climate.
- In 2014, the number of international students had been climbing.
- We should consider that tuition also rose that year overall, and according to the WSJ, 2017 was one of the few years tuition didn't see a huge increase due in tuition. Are non-Americans willing to pay for an expensive education, when they can get a comparable one elsewhere at reduced cost? I don't know the answer, but price could be a factor. Either way, the WSJ points to reduced enrollments.
- I know many Americans who've been questioning the value of US university education. At what point do non-Americans start to ask this as well? I can't answer on this, but if Americans are questioning their own universities (unrelated to Trump), it's possible non-Americans might for similar reasons.
This doesn't mean Trump won't negatively impact American universities; I think it's a little too early to tell right now and the trends we're seeing may be related more to price (per WSJ) and quality (WSJ and IHE).