Is there an Electrum based USB Distro?
I have considered building a electrum usb-distro but the problem is it would be hard to keep it updated after each new release. However if there is enough interest I might do so. 

Your best bet is to simply take a debian live-usb and install Electrum on it; you can follow the instructions for linux on the electrum site.

If you have any specific Electrum questions you are always welcome to join #electrum on freenode and ask your questions there.