You cannot really use batteries for mass storage of electricity suitable for a nationwide grid, that's just too expensive. On the other hand you can transport it relatively easily with minor losses, and it's pretty uncommon for there to be no wind in the entire United States. But even in a small area, wind is useful for generating a significant part, if not a majority, of the required power, and it can be combined with e.g. nuclear power that can provide a steady source of environmentally friendly backup power. During times of power surplus, you can pump water back up hydro-power lakes, which is a surprisingly efficient method of storage. With a smart combination of wind, solar, hydro and nuclear you can produce all the power needed with very few carbon emissions and little pollution.