Not American either, but in the US many schools use/used standardized admission tests (SAT/ACT) on top of things like HS GPA/grades.

There are many countries, especially in Europe, where entrance/admission tests are not a thing.

I worked in admissions for an Ivy League. We used a vibes based system based on how compelling a sob story you could concoct whilst staying on the good side of fraud. Ie you wanna aim for drug addict father black trans queer activist with autism etc whatever is on the NYT frontpage today. I know two companies whole line of business is just optimizing your sob story. Things are changing a bit now though, it did get a bit ridiculous around the years 0 - 4 AF (Anno Floyd). Core of the issue was always protecting legacy admissions and other grifts vs the deluge of Asian students with perfect test scores. I wish I was lying