Geographical Targeting in Adwords for Clickbank campaigns?

The vast majority of Clickbank products are available world wide but the question is…does targeting adwords campaigns (to say to US and Canada + UK instead of choosing just ALL territories) Increases or Decreases ROI?
The thing is that in theory if your keywords and ads are in english, only english speaking navigators will click on your ad, BUT, will english speakers in say…Russia for example really: willing to spend – or will those clicks just decrease your ROI.
P.S: I submitted a similar thread to the Clickbank threads area but got 0 good answers, so I decided to ask here.
Thanks

See original post by rickybuitrago