In the US, I think most places let you write in whoever you want. If they get enough votes, they win. Google "Lisa Murkowski".
The other problem is that unlike parliamentary systems, in the US we vote for multiple things and not which party/who your MP is. These are some of the things on the ballot:
1. President & VP 2. Senator 3. Congress Representative 4. Judges 5. Ballot measures
Unless each of these is on a different sheet of paper, counting them might be hard. Don't get me wrong though. I think that we should be using paper ballots. What does it matter if it takes 2 days instead of 1 to figure out who won.