In the United States, the majority of rental cars have automatic transmissions. It's not hard to understand why rental car companies made this choice anyone who knows how to drive can drive a car with an automatic transmission. But if you prefer manual transmission, you should mention that to the rental car agent when choosing your car.
In other parts of the world, manual-transmission vehicles are the norm. If you're an American traveling abroad, you may want to ask the rental car company if you can rent an automatic vehicle. This could be particularly handy when you visit a country like Ireland or England. In these countries, the steering wheel is on the right side of the vehicle and the driver operates the manual gear shift with his or her left hand.
Be aware that the rental car facilities may only have a few automatic vehicles available for rent, so it's a good idea to put in your request as early as you can.