I'm not an expert on this, but I think the JTF can get its numbers back up if it is a little bit more like it was in the past. A bit more hard-edged, more radical with a renewed focus on being anti-black culture along with being anti-muslim.
There seems like there are more American pro-Israel forums and facebook pages than there was in the past. That might lead to competition. I know that they aren't Kahanist, but they are still new alternatives for the Pro Israel Jew or Christian.