You will not be able to receive US programming on a Canadian sold radio. If you want to listen to the US programming, you need to purchase and register a US radio (US billing address etc). Radios sold in Canada cannot receive US programming as it is blocked by the software on the radio itself.
Not true. Whether you're able to receive the full US lineup on a Canadian bought Sirius radio, depends largely on the age of the unit. If you have a newer unit, there should be no problem whatsoever; if it's an older radio, it would depend on how old the chip in it is. Since you received your radio for Christmas, you should have no worries. All you need now is a US address and you'll be all set.