Keep in mind, before anyone can take the U.S. Citizenship test, they'd have to reside in the country for some time. Most often, they're already "Permanent Residents".
It's not like Italy, who'll take anyone.
I have to live here for 5 years (3 now I guess) to apply for citizenship from my permanent residency.
I'm not going to do that though because really. I'm Canadian, its basically American but with health care