When it comes to becoming a U.S. citizen, there is no differentiation among the applicants' native homelands. The rules for an Australian citizens wishing to become an American citizen are identical to those of a Brazilian, German or Indian applicant. In all cases, citizenship begins with legal permanent residency. Once residency is obtained, citizenship is only a matter of waiting.
Obtaining an Immigrant Visa
To obtain legal permanent residency in the United States, an immigrant must have an immigrant visa. Immigrant visas are different from non-immigrant visas in that they can turn into permanent visas or green cards. For example, non-immigrant visas such as student visas, tourist visas or temporary work visas cannot turn into permanent visas. That is, you cannot turn your student visa into a green card or change the status of a tourist visa by getting married or finding a job.
U.S. immigration law places procedural conditions on visas that must be followed. If you get married to an American citizen on a tourist visa, you must leave the country and then re-enter on a family member visa. Visas that can become permanent include work and family visas. Only permanent visas can lead to eventual citizenship.
Marriage to a U.S. Citizen
Marriage, either inside or outside of the United States, is grounds for a permanent visa. Australians who are engaged (not yet married) to an U.S. citizen can enter the United States on a K-1 fiancé(e) visa to get married.
Once married (must be married within 90 days of entering the country), permanent residency must be filed for to receive a green card. Australians who are already married to an U.S. citizen in Australia or any other country must enter the United States on a K-3 spouse visa and then file for permanent residency.
Residency in the United States
All naturalized U.S. citizens must fulfill a period of residency to be eligible for citizenship. The general period is five years, however, for spouses of U.S. citizens (K-3 or K-1), the residency period is only three years.
During the residency period, the green card holder cannot be absent from the United States for stays of one year or more without acquiring a re-entry permit and an Application to Preserve Residence for Naturalization Purposes (N-470). Those who do must restart their five-year residency period and, in the case of failing to obtain a re-entry permit, may be stripped of their green card.
Legal Requirements During the Residency Period
During the residency period, Australians and all other naturalizing citizens must comply by the laws of the United States and of their state of residence. Committing a crime, even a misdemeanor, can bar an applicant from citizenship approval. In many cases, a green card holder who is convicted of a crime must stand trial in an immigration court, as committing a felony is grounds for deportation.
Aside from moral behavior, other citizenship requirements include financial stability (proof of paid taxes) and knowledge of U.S. civics. As Australia is a native English speaking country, an English examination is not necessary.
American Citizenship by Birthright
Australians born to either an American parent or American grandparent have the right to claim natural citizenship by birth. Claiming citizenship is done through the U.S. Citizenship and Immigration Services (USCIS) by filing forms N-600 or N-600K (for minor grand children of Americans). In this case a citizenship interview and ceremony must be attended, and the Australian applicant must appear in person at a USCIS office inside of the United States.