Not sure why but I haven't looked at it myself, that being a US one.

These are global ones I believe, I've signed at least two of them. I'm started to get muddled now, what with global and UK and European ones - though I'm glad there's attention being paid:

http://www.petitiononline.com/stopacta/petition.html
http://www.stopp-acta.info/english/get+involved/petition/petition.html
https://www.accessnow.org/page/s/just-say-no-to-acta