A few other things to add:
FA for Publics - each state is definitely diff’t. Aralis is correct about Cali and the UC’s (info via a friend), but Texas allowed for residency for us, but each school had diff’t requirements. Be sure to talk to the schools in Mass that you’re interested in directly to find out the criteria. You may have to submit a ‘core residency’ form to establish eligibility.
FA for Privates - for Mass private schools, there may be state grant funds available (if you’re eligible for need-based aid). If so, you may need to go through the same process as for the publics. In Texas, some schools have a ‘core residency’ form that must be completed to determine if you’re eligible for state funds; there may be something similar in Mass. This is an inexact science and you shouldn’t expect the schools to handle it correctly. We had 1 school fail to recognize grant eligibility, one gave it automatically and the other required the ‘core residency’ form be completed. Be sure to ask about this.
Admissions - some schools treat folks like you separately, some as though you are international, some as though you’re a typical US citizen. As already suggested, find out from each school. From our experience Christian schools were more likely to treat you as though international, but some secular schools did. For example: Davidson didn’t have a separate app, but they treated the applicant as though part of the international pool. Some schools have you work with the intl adcon (such as Davidson), others with your normal state adcon, you just need to ask.
American University - American was unique among all the schools we’ve looked at. American treats US citizens abroad as a completely diff’t group and refers to them as ‘global nomads’, and they have separate application requirements. Probably specifically to attract the state dept kids living abroad. Whereas the Christian schools are likely targeting MKs living abroad (such as Wheaton and Calvin).
Freshman Orientation - Even though you’re American, if the school you decide on offers a special orientation for international students you should strongly consider attending. It may soften the landing.