while we are sometimes quite local and sometimes intergallactic

Siamo una familia internazionale, veramente. :D

I didn't try it but in English, "we are a multicultural family" would be a better translation.

Does "internazionale" have the meaning of "from another country" or of "of people from different countries"?

i believe the " We are one international family" should be also accepted as i think "una" can be number too, am i right?

"Ours is an international family"

I think some of the comments are confused. I'm pretty sure it's trying to say, not any specific family, but us at Duolingo are one big international family.