The situation in the US with international applications is very difficult. Only a handful of colleges consider international applicants without taking into account their ability to pay and guarantee them adequate financial aid if they are admitted. Understandably, those colleges are absolutely swamped with applications from international applicants who can’t afford college in the US without aid. And, since they also tend to be among the most prestigious US colleges, they also attract applications from tons of international applicants who CAN pay. As a result, it is super-competitive for international applicants at those colleges – which of course include Harvard, Yale, Princeton.
The factors you discuss improve your application, although you need to make certain that your counselor and teachers address them in their letters for full impact. Nevertheless, if the best you can do on the ACT is 31, and you are a native speaker of English, and you are not a candidate for an Olympic medal or a Nobel Prize, you aren’t likely to be competitive for admission to Harvard or any of its close peers. I am not saying don’t apply, but even without the prior application it would be a low chance of success, and with a prior application . . . it would be lower than that.
If you really want to go to college in the US – and I am not certain why you should care that much, by the way – your best strategy is still going to be a longshot, and a lot of work. You need to go a good way down the prestige ladder, to colleges where you will be a standout applicant in every way, and apply in the hope that you will be one of the two or three international applicants they decide to admit and to fund. You may need to apply to 20+ colleges (and even then, you may ultimately be unsuccessful). A number of them may admit you but not give you sufficient aid, which will be very frustrating and upsetting; you have to be prepared for that. You have to do some research to figure out which colleges admit even one or two internationals on full aid.
Meanwhile, it’s not like UK universities are so horrible. Your coursework will be very focused, but you can attend lectures widely and get a perfectly good “liberal arts” education, if that’s what you want. Since, in the final analysis, you may not have an American option, you really ought to devote some of your energy to figuring out how to make a UK college experience work for you rather than fantasizing about Harvard.