Enlisted Marine Corps ranks are broken down into three levels, Junior Enlisted, Non-Commissioned Officers, and Staff Non-Commissioned Officers. As a Marine moves up the ladder his or her responsibility and contribution to the mission increases.
Also, children born abroad to two non-citizen nationals or to one alien parent and one non-citizen national parent are eligible for non-citizen national status. This is so rare that the State Department does not even issue a certificate for it. Non-citizen nationals are delineated as such in their passports.
As of January 1st, 2014, yes, all U.S. citizens require a valid passport to enter Canada. This is the final regulation agreed to upon by both countries in 2013. If you have any questions specific to American citizens entering Canada, visit the U.S. State Department for information and updates.