that 3 million more popular votes won by Hillary. These 3 million popular votes are really tiny in our population, so tiny that it can be buried by our EC system. Otherwise, say popular votes difference is 10 millions, this number by no means can be cancelled out by our EC system. Basically our country is evenly divided.
Another point is you have to see our country as a structure on which our system is built on. (I am not against your view on popular vote, which is one angle). The foundation of this structure is county. This is map of election. Trump won 2400 counties and Hillary won 400 counties in this country. Which means when you visit one county in this country, nearly 85% chance you are in a county that voted for Trump.