Although it may seem so sometimes, but this is not the USA. This is the internet.
Now, sorry for marking words, I'm just a bit tired of people making that assumption.
I don't really care if people say Christmas, Hanukkah, or Jule, or whatever they may celebrate. But it *is* somewhat small minded to assume that everyone is Christian, or celebrate christian holidays, even though a lot of what today may be associated with Christmas actually have a hedonistic past, which is fairly common knowledge up here in the north. Carrying in the christmas tree in doors to your home for example, was done to hide from others the fact that you celebrated old hedonistic traditions (worshiping the nature and it's old gods) instead of the new christian ones.
Also, lets not forget all Hindu and Buddhism here. I'm pretty sure they don't care about christmas a whole lot either. There are a lot of religions and old traditions of celebrating and giving gifts to your close ones during this time of the year. Typically because in the northern hemisphere, the nights get longer and longer until they start getting shorter and daylight returns and spring is closing in. This is what many old religions celebrated. So just settle with wishing "happy holidays" and you pretty sure to be greeted back, no matter of others beliefs.