Most American Jews born in the mid-20th century, while clearly “off the derekh” (usually already one or two generations removed from Yiddishkeit) were likely to be Jews according to halacha. While intermarriage among non-frum Jews was high in that period, it was still well below 50%. At present, several generations late, given the high rate of intermarriage among non-Orthodox Jews, it isn’t especially likely today that someone with a Jewish name born into an other than Shomer Shabbos family is actually Jewish (remember that having a Jewish father means it likely the mother wasn’t Jewish), so in the future one won’t be assuming that a politican (born in the 21st century) with a Jewish name is actually Jewish (unless the person is Shomer Shabbos).