The only way your one vote has any chance of determining a US presidential election is if you sit on the US Supreme Court. Anything within a few hundred votes

The only way your one vote has any chance of determining a US presidential election is if you sit on the US Supreme Court. Anything within a few hundred votes will be decided by the courts. See Gore v. Bush. "It's not the people who vote that count. It's the people who count the votes." (Joseph Stalin)