Customer/Account visibility

We are global Organization and also have Oracle EBS implemented at most of our locations.  We have exported active customer ship to customer information from our EBS instance and imported into CRM assigning customers to owners based on territory assignment to sales reps from EBS.  We are using books of business to segregate data for each location in CRM.  This works well in our European locations since each location is a different operating unit, however, now that we are implementing for the Americans we have an issue.  In the US we have one operating unit and a ship to customer location can