Quote: Most (and by that I mean just about all) the people in the USA would only vote once even if it were as easy as you think to vote multiple times.
--Pete
Well than I am sorry about that remark. Than it means you truly are better people than us Europeans, and I sincerely mean that.
Further, I understand all your points. However, most things can also be done when using paper ballots. If there is this whole plot of people to rig elections they will be able to print some ballots as well, and have some people helping them during counting. Or just pay off the people that are counting votes, or pay off the people that call in the votes to the next person. It is all a question of doing enough checks in between.
When something is technically possible it doesn't mean it is practically doable or that there are people willing to undertake such action which contrary to casino fraud doesn't directly make you rich.