I realized this Christmas, though, that there are a couple American Christmas classics that could easily lead to a couple misinterpretations in Germany.
In the English-speaking world, to be "blue" is a commonly used term to classify someone's mood as sad. It's common enough that I feel confident about 99% of English speakers would understand the meaning if someone just randomly said "I'm so blue" without context clues or anything. So the title "Blue Christmas" is generally pretty self-explanatory.
In German, however, the word for blue (blau), when used to describe someone, carries a completely different meaning. Over here to be described as "blau" would mean calling them wasted, hammered, fall-down drunk, etc. Not quite the same meaning. But, I do think it gives the song a pretty good twist when you listen to it to mentally replace every "blue" with "drunk". I had a good chuckle, anyway. And oddly, it still kind of makes sense :-p
Rudolph, the Red-Nosed Reindeer, on the whole, is actually ok. It's just one little line in the often-overlooked introduction. To be more specific, it's another reindeer - you know, Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Donner, Blitzen. Although the last two are the actual German words for "thunder" and "lightning," respectively, they are not the magical beasts I'm referring to. The reindeer in question is dear old Vixen, whose name has much cruder meaning in German.
By "name in German," I don't mean the German version of the reindeer's name (they only have Santa and his reindeer from the English speaking world, so they all have the same names over here). The problem the word "vixen" in English is pronounced exactly like the German word "wichsen." Now, since I haven't completely overcome the standard American bashfulness/awkwardness when talking about sex, you can click the word for a link to the definition (I promise it is just a link to a dictionary!). Or we could just say if this reindeer's name in English was the same as the German meaning he would be Mr. and Mrs. Off's youngest son, Jack.
This really puts a kink (LOL! I did not even plan that, but I can't change it) in the plan when teaching this song to 5th graders. So, when the giggles wouldn't stop I had to give a little lecture: "In English the word is a reindeer's name, and since this is English class there are no other meanings right now!" It didn't totally work...
So be careful the next time you go caroling in Germany, make sure to double check your song choice before heading out.