Yup the Americans sure love to change their oil. While I do think many of them haven't "moved with the times" when it comes to changing oil (i.e they throw out perfectly good oil prematurely), the intervals we get on many euro-cars is insane.
The best thing to do is probably sending oil off for analysis and get a recommendation on intervals etc, but then again oil isn't that expensive and they might not factor in stuff like a MultiAir unit when advising.
Shell Helix Ultra 5W-40 is £30 for 5 liters off Opie Oils, so it's not too bad.
For the cost of an oil and filter I do a 6 monthly change and an annual full service on all my cars with the G it will also have an MA strainer annually.