Ancestry is a reasonable test of whiteness, I would think; those of predominantly European ancestry are white. Obviously Jews are a bit problematic in this paradigm (to the best of my knowledge, Jews of European ancestry would thereby be counted at white and Jews of non-European ancestry not), but they are not predominant in any of the areas in question.
This gets complex, though. You've got various sub-groups of "white". An Italian person looks considerably different from a British one; you can reasonably spot a Russian from a French person.