(yo-yo) Truism in the industry is that spares and repairs make up for the losses incurred in initial sales.
The problem with your assumption is that the KC-45 is not like a fighter such as the F-22.
The spares you’re most likely to need are avionics, refueling related equipment, and engines. All of which will be US sourced on the KC-45, and in many cases from the same suppliers as the KC-767. Airbus is only providing the airframe, and you don’t often need to buy a spare wing.
The main advantage to Airbus for winning the KC-X contract (again) is that they can then establish a final assembly location in the Unted States. They will use this final assembly point to also build A330-200F freighters for the civilian market, and have labor costs in US dollars.
Aircraft worldwide are priced in dollars, but Airbus has costs in Euros. So when the Euro is strong, the Dollar weak, they lose money on aircraft priced in Dollars. With a US assembly point, they can have both prices and costs in dollars.
This is why Boeing is fighting so hard to keep Airbus from winning the KC-X competition. They want to keep Airbus out of North America.