I WANT TO KNOW IF THE Atlantic International University IS LEGAL IN THE USA?
Regards
Popicho

I assume you are not US resident and need to apply for student visa in order to study in US.

Before applying to any school, check if they are listed here: International Student and Exchange Visitor Program (SEVP)

Not all schools can issue I-20 to foreign students, and you need I-20 to proceed with the visa issue.