I think you're overstating it just a wee bit. Take the total population of the 100 largest cities and you're barely cracking 50 million in a nation of 310 million.
For the record, you think Florida in 2000 was a goat****? Multiply that by 50. EVERY FOUR YEARS.
80% of the population lives in urban areas with populations of 50k or more and just the metro areas of NY, Chicago, LA, DFW and Houston have 53 million people.
and how would every election be like Florida in 2000? Reagan won by 8 and 17 million, Bush 41 won by 7 million, Clinton won by 6 and 8 million, Bush 43 won by 3 million, Obama won by 10 million. None of those would be even close to controversial.