如何獲得再入境許可？ How Do I Get a Reentry Permit?
A lawful permanent resident (LPR) normally may travel outside the United States and return;
however, there are some limitations. Your Permanent Resident Card becomes technically invalid for reentry into the United States. If you are absent from the United States for 1 year or more. Your U.S. permanent residence may be considered as abandoned for absences shorter than 1 year if you take up residence in another country.