It isn't normal for an American who has never been outside the US to use US/American currency. It implies a recent and significant foreign influence/experience and it could be military, doesn't have to be a foreign citizen. Cooper experienced foreign currency..
This is pure speculation. The bottom line is that it is an unusual request regardless of who you are or where you're from. To draw any conclusions is a stretch.
What we do know is that DBC had no discernible accent. That's it.
If I had to guess, I would say it's simply a phrase--if accurate--that is simply an attempt to be specific with respect to his demands. Furthermore, as those of us who are familiar with the Seattle and Vancouver, BC area in the 70s and 80s can attest, it was common for businesses in and around the area to accept currency from the other country at the current exchange rate. This was more common in Canada, but it happened in the US too.
Ridiculous. You call it speculation then proceed to speculate..
This is where this forum gets nauseating. Lack of critical thinking.
You argued for conjecture. Now reject it. Double standard or personal bias?
It would be extremely rare for an American without foreign influence/exposure to use the term US/American currency, that is very significant and denying it is denying experience, reason and logic.
95% of this case has speculation and conjecture... you can reject virtually everything if you want to apply a strict proven fact only standard. The very nature of the unsolved requires speculation and conjecture to advance it.