European Jews love to change their last names to Irish and Scottish last names. because it sounds very Anglo-Saxon "Christian".
John he's-not-Irish Kerry.
In every European country, the Europeans know and recognize the surnames that Jews have used.
In America, because we're only 245 years old, and have ancestry from all over the world, we're not familiar with the Jewish "changed" last names that they've used in Europe, so we have to look them up.
There are websites which list Jewish last names used in each European country.