FORM 8833的instructions提到DUAL-RESIDENT的情况
Dual-resident taxpayer. An alien individual is a dual-resident taxpayer if
that individual is considered to be a resident of both the United States and
another country under each country's tax laws. If the income tax treaty
between the United States and the other country contains a provision for
resolution of conflicting claims of residence by the United States and its
treaty partner, and the individual determines that he or she is a resident
of the forei
