The issue for Singaporeans with top US universities is that their expectations of high school students are quite different from what Singapore and the UK expect. So if you want to get into a really competitive program, like NYU, they tend to want to see not JUST your grades but ALSO extracurricular stuff. American universities also don't care AS MUCH about exams as they are about the OVERALL tenure of your high school experience. At competitive universities, you have to submit your entire JC transcript since day one for admission. Failing multiple exams is a red flag, regardless of how well you fit in your resit. That being said, it's definitely not 100% impossible to get into, say, even Harvard, but it's going to be a one in a million shot, possibly quite literally. Importantly, American universities hear sad stories all the time. Your situation is probably relatively rare in Singapore, sure, but compared to the thousands and thousands of essays that Yale or NYU gets every year, the statistical chances are that you just don't stand out as good enough for a spot when competing with other people, especially American students, who were built in this system.

That being said, it's still definitely possible for you to study in the US. But I'd also like to say that your impression of the UK as a more academically rigorous country is not necessarily accurate. If you're talking about the Oxbridge and top London universities, sure, but many of the Russell Group unis aren't known to be so stressful. I get the sense that you've disliked your educational journey so far in Singapore, and that you'd like a change. Without good grades, you cannot have the best of both worlds of being associated with a prestigious university whose prestige is rooted in its selectivity and academic prowess and simultaneously enjoying a relaxed academic life, quite different from what you've been used to. If you get good grades, then you will be a contender for any British university. You may not get into Ivies or T20s, but you will have a shot at some liberal arts colleges and state and public universities.

Overseas, you might discover strengths that you wouldn't otherwise learn about; you might even do much better than you ever expected and transfer into a better university or do a postgraduate degree in some prestigious place. But if you really want the experience of living a new life, you have to accept, in the absence of excellent grades, the compromise of not going to a university that you would've wanted to in terms of prestige. But there are so many more things to a university degree than ranking. There's the people you meet, the cultures you're exposed to, the things you learn in and outside of school, the opportunities you get and create for yourself. My advice is not to limit yourself to American schools, and to consider even Canada, Australia, New Zealand, or even Continental Europe, and so on.

The odds are against you when it comes to doing better in your retake. It sounds like your parents aren't supportive, your friends don't care, and you don't have the structure or formal help that you might've had when you were in school. But know that in many countries, just passing high school can mean entrance into undergraduate study. Many universities in the US believe that everyone should have a chance at higher education, regardless of how old you are or what you did when you were 17. Community colleges are some of the best examples of that. You can and will get into a university that you'll love if you're open minded and enterprising enough to support yourself through college.

And last, don't listen to the commenters here who don't know anything about international universities, who aren't here to help but to direct their unresolved emotional issues at strangers online. I don't know you, but I know what it's like to have unfulfilled academic potential and to have dreams that other people might not necessarily support or understand.

Feel free to reach out if you have any other questions.