Great input Mike.
When you say a debit card, you mean a bank card that you use with a PIN and that deduct the attached account automatically (we have this here in Canada and it is called Interac).
So you put that card number when you registered for the 1click payment method, but you if you are outside of the US (and I see that you live in Edinburg) you must purchase uniquely from the amazon.com site (i.e. not with whispernet). I agree with you that when you purchase from the internet you can avoid the 1click process.
What I want to do is use whispernet when I am in the US (i.e. 6 to 8 times a year). Then I fear that I might not be able to get it to withdraw from my GC account...
Have you tried through your kindle while in the US ?