Well rats! The old faucet came off all in one piece and the o ring must be either stuck inside there or gone. The copper pipe seems pretty smooth but the calcium build-up might have torn the o-ring.
Any suggestions regarding installing the new "universal" faucet using the adapter and extension tube that does not seem to fully tighten? The water squirts back at the wall when the new one is installed but I assumed it was because I cannot get it fully flush with the end of the adapter threads.
The directions say to cut the copper tube no longer than 2 inches from the wall before installing the new faucet. While I have a copper tube cutter and can easily do that, I was worried about doing that before ensuring that I can get the new faucet on and leak free first. Does it damage the o ring to slide the faucet on and off?