According to the Form instruction, your C Corporation is a U.S. person because it is a domestic corporation. Therefore, you should file Form 5471.
Below website link and citation are for your further reference.
Fiona Chen, MPA, Ph.D., CPA, ABV, CFF, CITP
For purposes of Category 2
and Category 3, a U.S. person is:
A citizen or resident of the United
A domestic partnership,
A domestic corporation, and
An estate or trust that is not a
foreign estate or trust defined in