I'm not sure what you are referring to by how the question is phrased. However, once an individual has earned the right to be called a US Marine (Graduating from Boot Camp), there are many military occupations (referred to as an MOS) that do require specific training and certification. To enlist in the Marine Corps, the candidate typically is required to have a high school diploma, and must pass a physical examination, and fitness test. There is another test to determine which MOS categories an individual might qualify for.
no license is required
no license is required
no license is required
No passport required
NO, passport required
If you are returning on a flight, yes. Otherwise with a birth certificate or driver's license is enough.
You do not need to do so. You can file it with your local county, but just need to be able to produce a valid marriage certificate if required.
You do not need to. The license and certificate will be issued by Romania.
Your birth certificate will not help you. You can enter the US from Mexico with an "enhanced" US drivers license, but only if you are traveling by sea or land, not by air.
No college is required to enlist in the US Marine Corps, a High School diploma is all that is needed. To be a US Marine officer, a Bachelors degree is pretty much required.
A recreational pilot license is required in order to pilot a private jet in the US.
Birth certificate or drivers license.