I Feel Bad About My Act Score?

I’m a high school senior in the US. I was raised in Latin America and attended a bilingual school for about ten years. I came to the US about two years ago, wanting to someday attend an Ivy League university. So, during my sophomore and junior years of high school, I took honors classes (such as Honors French and Physics, and AP Biology). I got a 4 on the AP Bio exam last year. As a high school senior, I’m taking AP Physics, AP Chemistry, AP Literature, AP French, AP Spanish, and AP Calculus. I have all A’s.
So I took the ACT at the end of last year and scored a 20. I wasn’t satisfied with such a low score. So, trying to improve my score, I bought The Real ACT Prep Guide and did two practice tests (timed). Weeks after I re-took the ACT, I receives the scores and noticed I got a 22.
I’m wondering WHY do I find the ACT so impossible to conquer. Could it be because I’m not a native English speaker? (I know, there are some kids who do better than I on the ACT. Could it be because they are more fluent in English than I am (since they’ve lived more years in the US)?) Could it be because I don’t prepare effectively?
I believe it’s too late now to be thinking of taking the ACT a third time since I’m half way through my senior year,meaning that’s too late to apply to a prestigious university.
If you’re reading this, I’d like to know your honest (unbiased) opinion about what I should do.
Thank you in advance.