I’m currently undocumented, but I’m a citizen of two countries that aren’t well-represented in the college admissions process (Haiti and the Bahamas). Would I get a boost in the admissions process?
Not a meaningful one. There are more multi-passport kids than you might think: my lot all have several, including a very under-represented one, and their schools (so far) don’t list them in their ‘where our students are from’ section (they could add 2 countries to their list at the current US college).
Depending on what your actual life has been it might be fodder for essays.
Happily, your actual record is very strong 
Based on an earlier thread, where you asked for chances to Ivy League colleges and Stanford, I would say not much, if any. It certainly would not make up for a deficiency in another area. With acceptance rates <10%, they can have their pick. They have no need to take an applicant from Haiti just to stick a pin in the map.
You story, if it’s interesting enough and well-written, is more of an advantage than your passport, IMO.
My own experience with a daughter at a NE boarding school is that there are tons of dual passports kids, a few being tourist babies. They aren’t undocumented of course, but certainly can put a pin on the map. My own daughter holds two passports, one from a small and not popular former Soviet country (she was adopted). We don’t think it’s a boost. Maybe adds to her interesting life story, but that’s about it.