I am not sure that is a significant factor. But the fact is that what you call "less powerful democracies" are definitely more conscious about external "pressures" (either political or commercial) and thus citizens tend to be more aware of political issues since a lot of the local political discourse has to do with "international competition" and its supposed local benefits.
If their local political consciousness exists (to a certain extend) within an internationaly minded consciousness, that would definitely be the main difference between them and american voters who are not usually told that they are victims of international competition since the myth has is that they _are_ the competition.
I'd put that in parrallel with Japanese voters who definitely are not made to have much clue about international economic issues (except when we talk about Japanese rice or American beef), which may be a reason why the political spectrum is so conservative, and not generally "smart".
Jean-Christophe Helary