Fact: Most frum Jews who left Europe between the 1700s and WWII to come to America were no longer frum by time they passed away in America. Their children, grandchildren and great-grandchildren have a strong possibility of not even knowing they’re Jewish. Most intermarried.
Fact: There were very very few rabbonim in America prior to WWI. Indeed, many shuls were led by laymen without having a rabbi. Even shuls with a rabbi, more often than not said rabbi knew precious little.