Of course, Congress can always take away that privilege at any time. See for example what happened in World War II with Filipino soldiers that fought on the side of the USA. In 1941 Roosevelt incorporated the Filipino army into the US army (the Philippines were a US colony at the time.) After the war they were officially US “veterans” until Congress passed the Recission Act of 1946 saying that they were not veterans and therefore not eligible for any benefits (medical, citizenship, etc.)
In 1990 a new law allowed them citizenship and in 2003 a law was passed giving Filipino World War II veterans living in the US access to medical care benefits for veterans.
You’d be surprised. The Navy kept calling me about their nuclear science program for about five years with a retort to everything I said. “We can help you get in shape”, “It doesn’t mean you have to serve on a submarine”, “Free education!”, “The chances you’ll be exposed to combat are extremely tiny” etc. etc.
– Find a job and get an H-1B visa, then file for an adjustment of status
– Marry a United States citizen or permanent resident
– Win the diversity lottery (I know several people who have, so the odds cannot be that terrible)
– Invest $500,000 or more into a business venture in an underemployed area of the United States
There’s also a pretty good program referred to as the Expeditious Natuaralization Program. It’s for immediate family member dependents of US Armed Forces members. (I don’t recall if it also applies to dependents of civilian employees of the government.) If the dependent has been admitted to the US for Immigration and the military sponsor receives transfer orders to a post outside of the United States, then the non-citizen dependent may be naturalized without regard to length of time in the US provided all other requirements for naturalization are met, provided that the newly-minted citizen joins the sponsor overseas immediately after naturalization.
During my time in the military, every instance where someone needed that program, it required a gentle reminder from the servicemember’s Congressman’s office.
There was also one case where the member’s wife decided that once she was naturalized, she didn’t have to bother with leaving the country to join him. The upshot of that was she was stripped of naturalization (because she didn’t comply with the requirements of the program), he divorced her, and I don’t know what else happened. If she’d been in the US less than the two-year mark, I imagine she would’ve been deported.