A foreign national can easily become a permanent resident if he/she gets married to a US citizen. Similarly, the US citizenship process for the spouses of US citizens, is simple. Generally, Green Card holders who apply for US citizenship must establish that they have been living within the United States for a five year period. But the spouses of US citizens need not wait for five years and they just need to remain in America as lawful residents for three years and meet the other requirements, to apply for US citizenship.
A Green Card holder who is not a minor can file Form N-400, Application for Naturalization, to obtain US citizenship. Similarly, he must have become a permanent resident before five years and must have remained as a permanent resident in America for at least five long years. During that period, he must have spent at least 3 years in America and he may not be disqualified if he had remained abroad for a year or more, during that five year period. This requirement does not apply to the spouses of US citizens and they may apply for US citizenship if they have been living in America as Green Card holders for a three year period. But they may not qualify for citizenship, if they had resided abroad for more than 18 months out of that three year period.
Similar to the other applicants, spouses of US citizens must not have criminal records and they must have maintained good moral character. They must be good in English and civics as they need to get through the US citizenship test. Likewise, they cannot file their US citizenship applications in any American state and they can file their applications only in the American state where they have been living for the past 90 days.
If the spouse of the US citizen who is applying for US citizenship is not currently living with his/her US citizen spouse, who filed an immigrant petition for him/her, he/she cannot apply for US citizenship. This requirement applies to the spouses of US citizens and while applying for US citizenship, the spouse must prove that he/she is still living legally with his/her US citizen spouse and must live together with the US citizen spouse until he/she receives his/her naturalization certificate. Moreover, the person who has filed Form N-400, must not leave the country after filing the naturalization application and must remain in America until he/she becomes a naturalized US citizen.
There are no changes in the application process and in the naturalization process for the spouses of US citizens, but they can apply sooner for naturalization and may not be required to wait for five years as the time that they had spent in the United States as conditional residents will also be counted.