Financial aid for international applicants is extremely limited, as boarding schools channel most of their resources to help domestic applicants, Given that you have a US passport (but be sure to state it as Atria suggests), you should not be in a disadvantageous position relative to other American applicants seeking financial aid. Conversely, your international experience in Spain and fluency in many languages may set you apart. Some boarding schools count American students living abroad in their international student statistics, so you could be filling multiple admission boxes. In short, your background could make you an attractive candidate. Best of luck with your applications Imartin!