Vanadium 50 is correct.
As an international student, your odds of being accepted are incredibly low. Not just at MIT, but anywhere in the US...assuming you need financial aid. At MIT, this is not an issue, because they are need blind and provide full need (only 5 other schools do that). Elsewhere, it is.
Understand that the 150 spots for international students at MIT is actually quite large when you compare it to the number of spots for international students at other schools offering financial aid, which are not need blind. After the ivy league universities, the likes of UChicago, MIT and Stanford, the next colleges in line with *substantial* international aid for international students are liberal arts colleges. And they too, have incredibly low acceptance rates for international students. Expect them to be below 25% - most likely below 10% - for international students, even if they have an *overall* acceptance rate that is far above that.
If you absolutely want to go to the US, then you should be prepared to take some loans. I wouldn't, but that's the way it is if you can't afford it. (who would've thought!) I really think it's not worth going into debt if you're looking at going for doctoral studies, as it is likely that you will be low on cash for most of your PhD. Actually, I don't think going into massive debt for university is even worth it all. But it is your responsibility to decide how much value you want to assign to a US education, or rather, US education at one of their most selective colleges.
Europe is an avenue worth considering. If you start learning German, you can go to Germany, Austria, or Switzerland, where tuition is rarely above 1500 euros per year. That is if there is any tuition at all. Most places in Germany only charge "semester fees", which are at around 200 euros. And you get to travel for free in the surrounding areas, get other student discounts and access to university facilities. And you get a top notch education too. You won't be spoon fed. It will be hard. But you can still succeed there. And the other good thing is it makes no difference if you do physics in Munich v/s Hamburg, at the bachelor's level. German universities tend to be of a similar standard, and it's only at the postgraduate level, where this matters, as some universities will have stronger research groups and/or industry connections in a limited number of fields.
Back to getting into a US college. Whether it's at UChicago or Macalester, your application needs to be able to *convincingly* answer the question "What's in it for us?" They know why you want to go there. Why should *they* want *you*, interhacker, running around campus?
The gist of it is you should be impressive. If you're faking it, they may or may not know. But ask yourself this: do you want to attend so badly that you will "fake" interest into one or two activities, and take it to the very top level? In all likelihood, you won't even have the motivation to take a "faked interest" that far. Which brings us back to what Vanadium 50 said: "If you're doing it solely to make your application look better, no. If you're doing it because you truly want to, it might, but then I would ask why you aren't doing it already?"
Also, your grades are fine. Most schools don't really care about the writing section, but it's incredibly easy to score above 700 on it. Look up Erica Meltzer. And take Math II, and make sure you get as close to 800 as you can on it. Same with physics. Most international students tick those boxes. Your grades just get you through the first round. What wins the round is how convincingly your application answers "what's in it for us?"
For e.g: if you're winning powerlifting competitions in your weight class, on top of being an excellent sprinter (for e.g 5-6 second 40 yard dash), this screams "potential football player". And it's also strange, because powerlifters are usually portrayed as those fat strong dudes (not entirely true). And it also shows that you've taken something as far as you can possibly take it: you like being stronger, you've trained hard and dedicate a lot of time to developing that strength, and you're now at the point where you're winning national competitions.
Just to put this out there: I once PM'd a girl from the UK (elsewhere) who got into lots of top schools, including Harvard, Yale, and Stanford, I believe. She had A*s in the 5-6 A-Levels she did, and was in the Olympic rowing team. That sounds very impressive, and it is.
But there are other ways to be impressive. For e.g, Cal Newport talks about a kid who got into Stanford (in his book How to be a High School Superstar - haha) by writing one or two game programming manuals which sold extremely well. He also made a "Pi Day" at school...where he just got people to bake pies and give them away or something.
He also talks about a guy who while doing the MUN at NYC I think...somehow ends up working from home for a big NGO and he did great there.
Of course you don't need to be that awesome. Not everybody there is like that, though every other kid probably has some kind of distinguishing attribute.
But the bottom line is that you are the one who gets to assign value to this. You're starting university next year. Do you really think a US education is that valuable? If you answer yes, then you better work for it. Also: MIT has a helpful guide for writing recommendations. Use it.
