Kind of a poorly-defined (undefinable?) OP, but there it is.
Any “perceptibly ethnic” surname that is found worldwide among descendants of emigrants but would be considered uncommon in their country/region of origin?
Like finding that McGillicuddy was common in Boston but (I know this isn’t true) rare in County Cork? Or that there were no Thibideauxs is France 'cause they all went to Acadia?
I suspect one probable example would be German/E. European Jewish surnames, given the small remnant populations of any Jews there. True?
Others?