<p>What is the difference in the "admission selection process" for an international student living in US already and a pure international living overseas? Does US internationals have any advantage or even disadvantage? Less competitive?</p>
<p>The admission process is roughly the same (you just have to fill out a different fin aid application). You're somewhat disadvantaged because you do not have an excuse for a low verbal score on the SAT, for a lack of ECs, or for subpar recs (if you have them). On the other hand, colleges will know your high school and they will know if you were at the top of your class or how competitive your school is (which is not the case for schools overseas, which don't have a school profile, class rankings, middle SAT score ranges...)
What makes admission so competitive among international students is financial need (-> no federal aid). If you don't have it, you're fine. Otherwise good luck!</p>