No statewide recount, much less a nationwide recount, would have been warranted in any of the nation’s 58  presidential elections if the outcome had been based on the  nationwide count. 

The state-by-state winner-take-all system is not a firewall, but instead causes unnecessary fires.
“It’s an arsonist itching to burn down the whole neighborhood by torching a single house.” Hertzberg

The 2000 presidential election was an artificial crisis created because of Bush's lead of 537 popular votes in Florida. Gore's nationwide lead was 537,179 popular votes (1,000 times larger). Given the minuscule number of votes that are changed by a typical statewide recount (averaging only 274 votes); no one would have requested a recount or disputed the results in 2000 if the national popular vote had controlled the outcome. Indeed, no one (except perhaps almanac writers and trivia buffs) would have cared that one of the candidates happened to have a 537-vote margin in Florida.