Fully aware of the KC-X contest, NG was the prime contractor but it was actually Airbus that did all the work.
The KC-X contest was only ran because Boeing got caught firstly trying to lease replacement tankers to the USAF at a rate which was several times more than they cost to buy, and then Boeing got caught in the first round buying the Airbus bid details from the US DOD procurement officer in charge of the bids.
Even with a US prime contractor and a US assembly line, there was massive uproar over the fact that Airbus had won the second round of bidding, before it got out back out to tender and Boeing magically found a way to make the 767 offering several billion dollars less than their previous bid...
There is no way the US political arena would accept a non-American plane as AF1. Which raises an interesting problem when the next replacement comes round...