The United States should ban all dirty energy resources and put all funding into alternative energies. We reached the peak of the earth's oil in the 1980's, meaning we are using more than the earth naturally produces. Coal plants cannot operate without oil, rendering both methods useless in the near future.
While coal plants should eventually be gone from the country, it should not be an outright ban to begin with. At first, it should be an imposed limit that will eventually lead to permanently phasing them out of use. An immediate blanket ban would cause much more harm than good, there first needs to be a backup infrastructure in place.
We need coal for many things--that's just the way it is. If we ban the plants now, then we will leave ourselves in the lurch. What we need to do is slowly phase out coal energy in favor of more renewable energies. When coal is no longer in demand there will be no need to ban the plants...no one is going to bother running one if no one will pay for it.
The US does need to work on alternate sources of energy, such as nuclear power. However, banning coal plants would put entire regions (such as West Virginia and large swathes of Pennsylvania) under serious problems. You cannot just simply shut down an entire regions main source of income, environment or not.