Geothermal is a stable & plentiful source of clean energy available all around the world, including in the United States (especially in the West). But that industry is still in its infancy and very little of that resource's potential is being tapped (a bit over 10 gigawatts worldwide, with about 3 of those in the U.S. and 2 in the Philippines). Hopefully this will change over time, as we phase out dirty power sources and as the cost of getting heat deep underground falls.
To give you an idea of the potential of geothermal power and of how far along we are, I'd like to share with you some great maps from the National Renewable Energy Lab (NREL). The first one (above) shows the resource potential for the country, with the redder areas being more favorable for deep enhanced geothermal systems (EGS), and dots identifying known hydrothermal sites. Note that there are many hydrothermal sites in Alaska even if there's no data yet on EGS potential. You can see a large version of the map here.