90% of America’s Jews stem from the immigration wave of 1890-1910. They came from Eastern Europe and came largely against the advice of the Rabbinate.
It is no wonder that so many of them and their progeny became non-religious or token-religious(reform, conservative etc.).
Religious Jewry stems from a tiny minority of those “fiddler”generation and largely refugees, escapees and survivors of Hitler and Stalin that came in the 30-50’s. They are popping out babies and are not intermarrying, and are becoming more observant.
Imagine how religious Irish and Italian catholics would be if the Pope condemned immigration to the US in the 1890’s only Sinead Oconnor and Sacco and Vanzetti typeswould have come
And if they'd listened to their rabbis, they would have stayed and been slaughtered.
So much for listening to rabbis.