Why is the internet so slow in the U.S?

In some countries, the internet is considerably faster. One of my Asian friend's was telling me about how it was much better in South Korea. Why is it that some parts of the U.S. don't even have broadband internet available? It seems that internet users in other developed countries have access to much more bandwidth. What's up with that?

Cables to carry data cost money to lay and America has lots and lots of space for them to traverse.