Every candidate is eligible for a nomination from the Vice President. Each congressional staff has its own parameters for determining if you are a resident or not. Additionally, those candidates who have a parent that retired from active U.S. military service is also eligible for a Presidential nomination. Please apply to ALL nomination sources for which you are eligible, as this will enhance your application efforts. You want as many nominations as you can get.
Most nominations are competitive.
A senator or congressman provides a list of 10 names and USNA selects the best one. If you are on several lists, the chances of you being the most competitive on at least one list significantly improves. That said, students in a non-U.S. structured school are advised to submit a letter of explantion detailing the course progressions through the grades, any use of national exams, the significance of the grading system, along with any other explanation you feel will assist the Admissions evaluators. Each year, there are several opportunities available for certain non-U.S. citizens to attend U.S. service academies. The U.S. Naval Attache will be able to advise you as to whether your home country will be eligible to submit applications of their citizens to the Naval Academy via the U.S. State Department .