Hello! I also find Christmas decorations around my neighborhood. The illuminations are beautiful and people feel jolly to see them. What's wrong we are not christians!
We Japanese have been influenced by foreign culture from our beginning and that became our nature. It doesn't bother us we borrow good things from abroad. In the Meiji restoration, we changed our old systems so drastically and quickly while China had to struggle to change them. That is because, I think, our culture was a borrowed one and for China, it was original to them.