Why are Ohio and Florida so important? Is it just because they have been known to vote for candidates rather than just Republican or Democrat?
Each State get a number based on population.
California gets 55 v Vermont of 3 because California has more people. So more weight goes towards it.
Winner takes all, majority wins.
So even if 49% of people vote for the other guy, tough.
Some States are biased towards one side and one the other.
Typically rural areas votes Republicans, middle age, white middle class americans typically, Texas.
Where cities population generally votes democrats - New York.
Generally, even before Obama, Blacks and Latino votes democrats. It was the democrats after all who brought in the Civil Rights Bill for equal rights for blacks. Even Clinton and Kerry over 80% of the black votes, it has little to do with Obama being black getting the black votes.
Therefore the demographic of the people in that state does have a huge impact and influence on the result.
There is also the ID criteria, you need an ID to vote, and the US has no ID system and a lot of people don't even have Passport. So it is down to having a driving licence and that normally translate to having a car and that means a lot of poor americans don't have (1 in 6 is under the poverty line), so you can argue the voting system is biased against the poor.
Then you have States that is flips between each side historically, it is these states that matters the most.
You need 270 votes in total to get in the white house.