I dont have the key to open my iphone 4s to get the sim card out, and I want to replace it with my daughters sim card, can I use any other object to do so?
You could try using a paper clip - bend one side of the paper clip straight out (opened) so that you can use that end of it (the paper clip) to insert into the small SIM tray eject hole on the iPhone, that should eject the SIM. I've had success with this in the past when I've needed to remove the SIM card
I don't know why Apple only includes them outside of the US, its an odd thing. fortunately I have spare SIM ejectors from other phones on my keyring for rapid phone changes.