The Natives are only said to have come from Siberia, but it is only a theory. The Natives of Mexico were a bit darker, and looked less Siberian than the Natives up North (U.S., Canada). The Inuits in Canada for example, they have a very Asian look to them, but the Natives of Mexico looked a bit different. Most Mexicans like myself are Mestizos, I don't know if a Mongol could pass for a Mexican, I'm Mestizo and I don't look Mongol or Siberian or Asian one bit (look at my icon). Since most Mexicans are Mestizo, we're carrying some European blood, which changes our appearance a bit. But overall, if the Natives DID come from Siberia, then we have a similar genetic make up, so maybe yes. As long as they're Asian features aren't too prominent, they probably will be able to pass as a Mexican. So yeah…

Yes. But you could find people from almost anywhere who could "pass for" Hispanics.

Some Mongolians do look rather like Navajos and the northern tribes. Then again, some look almost Caucasian. It's a mistake with any country to envision a single pure genetic line. Rather, there are many tribal lines that are frequently interwoven inside and outside of a country's borders.