One of the major differences is that if a state government is being evil then you can just move to another state. This is a far more effective manner to control the behavior of the state then democracy because it affects their tax base, and this is something they actually do care about.
AS far as corporations like ATT and Comcast it is important to realize that:
The USA is a mild-moderate level fascist state. Fascism, being a right wing off-shoot from socialism, is were you have corporate and labor interests working together as part of the government to direct and control the economic activities of the country. Which exactly describes how this country is ran today. The biggest difference between now and Italy of the 1930's is that instead of a single dictator power is divided up between two major political dynasties.
Companies like ATT would of never existed and gotten large if it was not for direct collusion with government interests. Things like regional monopoly grants, special legal privileges, grant money, FCC, patents, and so on and so forth they could not be what they are today.
Now I am not saying that corporations are your friends or that State governments are easy to control. Pointing out that things other then the Federal government are terrible does not make the Federal government any less terrible.
What I _AM_ saying is that CISPA is fucking evil and if it passes the Federal government will abuse it at every opportunity for political and economic reasons and it will do nothing to help make us safer.