Geothermal energy potential of America

Probably the most eco-friendly power source that I am aware of is geothermal energy. The only effect it has on the environment is from the holes that are drilled into the earth to harness said energy. Now for long term effects on the constant cooling of the earth I am not sure. But as long as we have global warming I see no way this would be a negative effect on our environment. What is more this report tells how underdeveloped this market currently is in our country.