I agree with the others Thande, it makes more sense to use a general scale instead of "in context", because the latter really skews up perspective.
EDIT: Don't get me wrong, this is a great idea, but there's a slight problem in the implementation. It really doesn't make sense to show France and Canada as more right-wing than the United States when we all know that they're not.
Also, historical versions of this map might get a bit sticky considering that you couldn't show colonial posessions easily...
I disagree completely. Political spectrums (spectra?) only make sense in context. Saying an American party is "to the right" of an Asian one makes little sense when the two parties are situated in different political cultures, move within different constitutional frameworks, tackle different issues, appeal to different electorates, etc. etc.
Deciding whether a party is more to the left or right within its own political culture is a fairly objective task. Deciding how leftist or rightist the parties are compared with one another, or with an arbitrary global scheme? That's speculation.