Americans vote ignorantly because they willingly limit what they research because there is little incentive for one person who cannot individually make very much difference. This also explains why information from another viewpoint, or party, is rashly dismissed out of hand without consideration or deliberation, for mere convenience.

Listen to this short podcast from CATO for the interesting analysis which has alot of merit.

This is where Democracy fails, and why Presidents (like Bush) can be elected with less than 23% of potential voters (about 50% eligible do not vote for various reasons, including disgust):

the rational decisions of individuals create a dysfunctional collective outcome

I think people are too busy earning a living to give a crap.

Another side of it may be information overload. When people are barraged with information they tend to shut it down and simply ignore it all. You could spend all your waking ours trying to become "informed" and be unable to a) get through it all and b) sort it out.

It is also difficult and requires so much work to separate truth from propaganda.

i think that people today are confusing availability of accessibility to information, with knowledge.