I will be in Amsterdam for a week and found this on their public transportation website:
"Identitycard
Weekly and monthly season tickets are only valid in combination with a public transport identitycard ("stamkaart"). Only annual season tickets are issued as single plastic cards carrying your name, date of birth and photo, so there is no need for a separate identycard.
If you need a public transport identity card and you do not yet have one, it is available free of charge at GVB Tickets & Info and post offices. To obtain one, present a valid identity document - a passport, European identity card or driving licence with photograph - plus a passport photograph.
Public transport identity cards issued to 4-18 years olds must bear their date of birth, filled in at the time of issue and legible when the card is used.
A public transport identity card is valid for five years."

If you have an identity card the weekly (starting any day) cards are 11.45 Euro - a bargain. Since it says that a passport is acceptable an American could get one? Is this similar to the Carte Orange in Paris that they really don't want you to have, but will let you?
Any advice would be appreciated.
Judie

This Website provides some additional helpful information.

Ann