Is there an Electrum based USB Distro? I would like to use a USB with a Linux distro, ideally with Electrum. The advantage of this is that the USB does not need to contain any information, just entering the seed would be enough, which provides extra security in my opinion.

Is there a distribution which does this? or there an instruction on how to do this?
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.