I would say it's more than that, TF2 also has a considerably different tone than Overwatch since it doesn't take itself seriously. TF2's cast contrasts with most of the Overwatch not only by having all male characters, but also that all of them are varying shades of homicidal maniacs. TF2's overall presentation is very slapstick and violent, akin to something like the Itchy and Scratchy show from the Simpsons. Just dumb, brutal, fun.

Well, TF2 has a pretty international cast.
A german
A russian
Three Americans
An Australian(Actually New Zealander)
A black Scot
A Frenchman
Something Unknown.