There's also the possibility that other countries have more robust voting systems so there is less to complain about. Do you think voters wait in line for five hours in Germany, or get turned away from booths in Scotland? Voter turn out is slightly larger in both countries compared to the US, so apathy probably won't explain fewer complaints. It's more likely that the lack of a US national standard system permits more screw-ups and maybe occasional outright abuse.

*(Scotland 64%, Germany 68%, US 55%)