Ivy League schools and other “top 20” universities are reaches for pretty nearly all very strong students. As one example, a few years ago Stanford included an article on admissions in their alumni magazine. They estimated that 80% of their applicants are qualified to attend. They accept closer to 4% of applicants.
However, there are a large number of very good universities in the US. Make sure that you apply to safeties.
If you do get to attend an Ivy League university, or even if you don’t, you will find a lot of very good professors, and a few bad professors. You will need to deal with the bad professors.
Also, whether you get accepted to a “top 20” university or not, you will probably never know for sure why you either got accepted or didn’t. Those of us who did attend a highly ranked university can guess what got us accepted, but we are only guessing.