Earlier quoted context omitted.
I think there is a difference between having cultural values and believing in a deity. We can expand the definition of religion to include those sets of cultural values, but then I worry that: a. the word religion loses meaning b. someone who was raised in the Islamic world and comes to the States and converts to Judaism can never stop being a Muslim? Even if they weren't one to start with? That seems absurd to me.
I'd suggest you look at Bellah's Civil Religion in America (1967), which suggests that certain ritual practices, e.g. rising for the national anthem before a sporting event, are religious in nature. And not that it's particularly definitive, but I'd note that cult and culture share the same Latin etymology. "Just as Thanksgiving Day, which incidentally was securely institutionalized as an annual national holiday only…
I've already read it. I agree that there are implicit religious values, perhaps even pseudo-religious, I disagree that it is an actual "religion" as such.
Nor do I particularly subscribe to American civil religion itself.