Write the District Attorney's office and explain in detail what you were told and that your intent wasn't to violate any part of getting past the situation. As you have no intention of any immediate trips ask for time served or offer to pay a fine or perform a service in the UK. If you enter into the US at any point of entry you will most likely be flagged. It's up to the DA's office if it's worth their money and time to have you extradited. It sounds like this was awhile ago & not a very seriously situation (the community service not the DUI) so I'm doubting they would spend the money and time to have you sent back.