Jack Werthheimer (provost of Jewish Theological Seminary) writes on Jewcy.com:
Pick a single religion and a single people. It will save you much grief. I hope the religion you choose is Judaism and the people with a claim on you is the Jewish people. Your wish to create a Jewish identity mixing multiple religious traditions is a fantasy, and you know it because of the very ways you think about yourselves—“FrankenJews,” “mongrelized” are terms you employ to describe your fractured selves.
No authentic Judaism can be built on the religious syncretism you demand. And no concept of Jewish peoplehood ought to be capacious enough to approve of the premise that Jewishness has merely a vote but not a veto, a phrase, by the way, coined by Mordecai Kaplan and the Reconstructionists in reference to Halakha, but not accepted by the Conservative movement.
So to answer your two questions directly: “Has America annihilated Jewish peoplehood?” It has eroded the willingness of a significant sector of your generation to take responsibility for fellow Jews.