My two cents is I think the mismatch between the UK and US bachelors-level higher education systems, which in turn explains the mismatch between the A-Level and typical US college-prep curriculums (as in, A-Levels are designed to prepare students to attend UK university courses, and the US college-prep system is designed to prepare students to attend US colleges), can in fact be an issue sometimes for A-Level applicants who apply to US colleges.
But it is a surmountable issue, obviously, because some students from A-Level systems do in fact attend US colleges, including the ones in the athletic conference you mentioned, and many other great US colleges.
OK, so I would suggest the more useful question is what does it take to be a strong applicant to US colleges if you go through the A-Level system? Of course really good marks in that system. But then I think you are right that for the sorts of colleges you mentioned, they are also looking for people who understand and value what is called the Liberal Arts and Sciences tradition.
In this tradition, at the undergraduate level you are not just studying some one course, you are going to study a variety of different things outside of what we call your major. And in fact, those sorts of colleges are often on an exploratory model, where you don’t even declare your major for up to two years after you start–very different from the UK system.
So you can be thinking in advance about whether that is something you really want. Like, it takes at least a year longer to get your bachelors-level degree. And you usually can’t just focus on a narrow set of things you know you like and will do well at. And that may not actually be something you want.
And you don’t have to decide now. But if it ends up you DO want it, then over time you can think about how to evidence that interest. Like, if you do just do STEM A-Levels, how can you show through your activities and such that you are in fact interested in non-STEM stuff as well? Reading and writing and arts and so on. Interests in stuff like that don’t have to be limited to a class, so you can think about how to keep all that a part of your life as well.
And this is just the academic part. The sorts of US colleges you are talking about are what are sometimes called residential colleges, and they believe that the non-academic aspects of being at a residential college are integral parts of the learning experience. So, they also want to know you understand and value all that, and are going to contribute in one or more ways yourself. Again, often people address this in part through non-academic activities, but you should also be aware they are interested in you as just a person–are you kind, caring, nice, maybe a leader or a role model for your peers, and so on.
Again, I think some people end up thinking that is really a bunch of nonsense, they can’t quite believe these colleges really care about all that, don’t they just really care about individual achievement, particularly in academics? Nope, I assure you they really do care about all that stuff too.
But if that actually appeals to you, if that is your vision of a great undergraduate experience as well, then you can again just start implementing that in your life–through organized activities, but also informally in how you relate to others–and that will help prepare you for these sorts of US colleges.
OK, that is a lot, but again these are different systems, so it makes sense there would be a lot you need to do to jump tracks to the US system rather than the UK system. But it is all doable, as long as you truly understand and value all that yourself.
And if not–you can stick with the UK system, which of course is excellent in its own way. Or, alternatively, apply to the sorts of US colleges which are less likely to be very picky about all this, as long as you have very good grades and can pay.