A long time ago I remember playing online at USCF. Then it was gone.

What happened to it?

One word: engines.

Check this article out: Is Technology Wrecking Chess? - Associated Content

USCF was late getting into the online chess market, and by the time they did, there were too many other good sites for it, so they couldn't compete. They eventually gave up, and I believe they're now sponsoring certain events through ICC, such as the USCL and other stuff.

--Fromper

Aren't they affiliated with World Chess Live or whatever the heck it is?

Yes, WCL has USCF tourneys on there, but only for quick rated, of course.

World Chess Live for more information.

See the NYT article, Sunday CHess Column Jan. 30, 2008 by D.L. McClain:
Is the United States Chess Federation in Trouble? - Gambit Blog - NYTimes.com
Not exactly about the Thread or maybe it is. The USCF is going broke.
Last year $42,341 in the red.