ujm, a quick google search reveals a YWN article “Talmidim of the Philadelphia Yeshiva say the ‘Pledge of Allegiance’ and sing the National Anthem before their graduation ceremony.”
Stephen Flatow writes: .. late Rabbi Avigdor Miller. A student asked, “should we celebrate July 4th?” … He answered “yes,” in order to show we “appreciate the great gift of America.”
I also wonder about early yeshivos, and also times when observant children were going to public schools and were exposed to civics there.