Do any of these other countries have the local / state / federal government separation nightmare of the United States, or do they have the same voting standard applied unilaterally for all citizens regardless of location? If not, then they aren't apples to apples comparisons. The American system is 50 different legal bodies, which means 50 governors, 50 senates, N local governments, all doing their best to muck up the system to bend to their own political goals. It's designed to be complicated, which means there can't be an easy answer without re-wiring the entire system.