Okay, main thing is the difference between a)an IB class, b)an IB exam, and c)an IB diploma.
In the US, a) is the only one that certainly affects your prospects at some colleges. With things like the Common App, the colleges will know about b) and c) (candidacy), but as far as I've seen, those are not established factors in admissions.
Many US colleges say they look at IB and AP
classes the same, but I don't think any say that they look at IB diploma candidates the same way as they look at people who have taken a certain number of AP classes.
Again, I don't think any give a lot of extra consideration to diploma candidates, and even if they do, the trends aren't published/discussed enough for us to evaluate your chances based on that. The US mindset pretty much separates earned/predicted IB diploma points from college admissions.
However, as an international, your counselor is encouraged to submit more information about you and IB, so it may be used more for your admissions case than it is for domestic applicants. I just don't know exactly how it works, but I don't see how a college would consider it fair to give internationals a lot of advantage over domestics for IB exam and diploma scores, so I'm not going to get your hopes up even if in reality they should be up.
For MIT:
MIT Admissions: International Applicants: Helpful Tips 
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