One reason why more American companies buy more wind energy is because of its availability. Depending on the weather, you can get more wind energy than solar, since at night, solar energy can't be harnessed anymore.
Another reason is that wind turbines are more efficient. They can harness more energy because of the wide span of the turbine and the height from the ground. Whereas, solar energy needs more semiconductive materials which produce a lot more waste and requires larger area.