Actually 241 M eligible to vote and 129 M actual 2012. Apparently this time it skyrocketed about 5%. Canada is around 68.3%
Here is a quote from PEW research
" U.S. turnout in the 2012 presidential election was 53.6%, based on 129.1 million votes cast and an estimated voting-age population of just under 241 million people. Looking at the most recent national elections in OECD countries, the highest turnout rates were in Belgium (87.2%), Turkey (84.3%) and Sweden (82.6%)."