As a general rule, the United States treats its prisoners well. Generally the reason behind this policy is that you want to encourage your enemy to surrender (German soldiers actually fought in the Last Days of WWII to get to the West to surrender to the West). However, as in all wars, treatment of prisoners was not always humane, either then or now. You have to remember that the media would never have been allowed to air allegations of abuse against German prisoners as has happened in the case of Abu Ghraib.