Is there such thing as a race?

Nope.

Yes.

"Are White Caucasian, Hispanic/Latino, Asian and Native American really ethnic groups?"

No, ethnic groups are things like Chinese, Russian, Ethiopian, etc.

Races are like white, black, East Asian, Native American, etc. Races are made up of various ethnic groups.

Hispanic/Latino is not a race. Hispanic means Spanish speaking, and Latino means Latin American, which just refers to the countries/territories in the Americas that speak Latin-based languages. Any race can be Hispanic or Latino.

White looking Mexicans look white because they ARE white. They are of European descent, which is not uncommon for Mexicans, considering it was the Spanish who colonized them. Spain is in Europe, if you didn't know.

In fact, yes. E.g., natives of the Americas have a U shaped jawline, whereas Caucasians have a semi-circle one. Natives have larger protuberances on their jaws to anchor stronger tends, to make it easier for them to chew meat. Native bones also age slower than Caucasian ones. And, so on. There are many of these tiny differences amongst the races. However, many of what you mentioned are ethnic differences, not racial ones. There are 3 races - ALL humans are one of these three (or, mixes of the three). And, no one race is better than any other.

Of course, if "racism" exists, and different racial features exist as well, then race is real. Enough said.