I would comment that the supply of O neg red cells in the US is NOT limitless and can be problematic. My hospital is in a region that is fortunate to be a net blood exporter, which is great for our local blood supply most of the time. However, there are always a few times a year when I am unable to receive or maintain a full stock of O neg because of high demand in my region and across the country. In some areas of the US it's a much more common problem. If the supply isn't there, we can be (and have been) forced to give Rh pos blood to some Rh neg patients who are not traumas, but who do need transfused urgently (GI bleeders, extreme anemia, etc.) in order to reserve the Rh negs for females of child bearing age and children. Maybe your trauma case won't make an anti-D, but my patient on Plavix with the GI bleed will and he/she may very well need blood again.
I think that it's important for us all to remember that trauma cases (and surgical cases gone haywire) utilizing large volumes of Rh negative blood have the potential to have an adverse impact on the care of patients outside the ER and outside the walls of our facility. So when you say that it's easy emough to get blood from Wisconsin, remember that patients in Wisconsin (or whichever region responds) may be the one feeling the bite. (And no, I'm not in Wisconsin.) That is why the issues of blood management and blood utilization are so critical now. There are studies out there on all kinds of related issues and more being done every day, making what we did 10 years ago, or even 2 years ago, questionable. What may be best for one single patient on one single occasion, when multiplied to thousands of patients, may not be good for universal patient care. We have to start thinking big picture. That is our challenge.