Are the natives of America mongoloids?
Under that racial classification, yes, at least most of them
are. Native Americans descended from somewhere around the Altai
mountains. Altai people are Mongoloids.
The Arctic Americans are neo-Mongoloid, and are recent arrivals
from Asia.
However, it may not be a good idea to classify people based on
Mongoloid/Australoid/Negroid/Caucasoid/Capoid, as the system is
arguably outdated.