This exists ( https://www.state.gov/document... ). A sizeable volume of requests are processed every year. However, some US judges don't want to use the official channels, I suspect because they are egotistical enough to think that their writ applies outside US territory. I don't mean to knock Americans, this is just human nature. An Irish policeman recently was recently in the papers for cooperation with the FBI to get Facebook to do something that could have been done much quicker by just asking the company's Irish branch office.