As somebody who hates Americanisms with a passion I caught myself out a couple of days ago saying Xmas instead of Christmas. I wondered What do other ABers think about this?
As they are both pronounced the same I can't see your confusion. It is certainly not pronounced "Exmas". It is not an Americanism; the symbol X is widely used by theologians as shorthand for "Christ", especially when taking notes in lectures, so in effect there is no difference in meaning and no disrespect.
I am not a believer but have always found this abbreviation obnoxious. However, I believe it is only meant to be an abbreviation when written and not a spoken one. Sure someone will correct me if I am wrong.
Chrimbo is horrible too, even more so in fact. Where on earth did a word like that come from. If Christians are going to celebrate the birth of Jesus then keep it as it should be.
It always make me laugh when "Christians" think that Xmas is blasphemous, disrespectful or whatever and just furthers to reinforce my opinion that the vast majority of people who claim to follow the Christian religion really know next to nothing about it...
From a practical point of view, why write six letters where one will do? As I have said, christian theologians must have to write the word "Christ" many thousands of times, so came to adopt the X (really the Greek letter Chi, initial of Christos). At some point in the past this tradition has spilled out of thee theological colleges and into the public domain.