Just how many grandchildren of Jews, especially when the Jewish grandparent is "only" a Jewish grandfather, are actively Jewishly engaged in the West, including without any conversions to Judaism?

I’m wondering if US Reform synagogues contain a lot of people with “only” a Jewish grandfather, for instance, and also whether they would actually be willing to accept someone like me, with a Jewish paternal grandfather and three gentile grandparents and who has a Jewish name and was raised Jewish until almost age nine, back when I still lived in Israel (which is where I was born), before moving to the US and being raised secular since then.

I know that a lot of ex-USSR people with “only” a Jewish grandfather are Jewishly engaged to some extent or another because a lot of them ultimately end up moving to Israel. But very few Westerners seem to be interested in immigrating to Israel as the grandchildren of Jews.