When these two concepts of ethnicity come into conflict, how can I explain the difference to someone who isn’t familiar with these cultural perspectives?

In Brazil/Latin America, being Latino usually means that you were born and raised in Latin America. If you only have Latin American ancestry, many people in Latin America would not consider you Latino. Their words.

Here, “Latino” is understood as more of a sociocultural identity. So it’s about growing up + being born there.

It happens with ethnicity in general.
if you say “I’m German because my grandpa is german”, many people would be ???. “Italian born in Miami” sounds crazy here.

In the U.S., on the other hand, it’s very common for people to refer to their ethnic background by saying things like, “I’m German,” “I’m Italian,” or “I’m Korean,” even when they’re American citizens.