I grew up on Long Island in the New York City area. The KLEIN name was common enough, several pages in the phone book with this spelling alone, that I don't remember anyone ever questioning me about the spelling. I've been living outside of the New York City area for almost 19 years and it seems that few people know that KLEIN is the "right" way to spell KLEIN.
I say the "right" way because I think it is the more common spelling and it is also the historical spelling. The word klein comes from German for small. I've also seen it in Flemish subtitles...Flemish is based in Dutch with has similar origins to German. KLEIN is the spelling used by my great-grandfather Abram when he departed from Hamburg. He wasn't German...his last residence was listed as Kovno, Russia which is Kaunas, Lithuania but I have no evidence to prove whether he lived in the "big city" or a nearby town. Yiddish has a basis in the old High German and many of the Jews of Eastern Europe have ancestral roots (several hundred years further back than I'll ever be able to trace) in the region that is now Germany. This is why so many Jews have German sounding surnames. KLEIN is not only a Jewish name...it's a name that anyone with ancestral routes in this region could have without regard to religion. In Eastern European records I need to look out for the spelling KLEJN.
So where did the spellings KLINE and CLINE come from? Well, I can't speak for all of the spelling changes but my understanding that these names were originally spelled KLEIN in America but were changed during the world wars when people were trying to hide their German heritage. These are the types of name changes that make me giggle. The name sounds the same for all three of these spellings...was anybody really fooled by this. Maybe, who knows.
I find that many people now assume that when I say KLEIN I mean KLINE or CLINE. It's fun sometimes when I walk into CVS to pick up a prescription and the clerk asks for my name, I say KLEIN, and they go to the C bin without asking me the spelling. I like see how much time they will waste before they ask. Then they will ask, I'll say K-L-E-I-N, and they start looking for KLINE...all they heard was K instead of the C they were looking for and didn't bother listening to the rest of it. And then there are the instances when people see KLEIN and say CLEAN. My dad actually received a letter once addressed to "Mr. Clean."
When I travel outside the US I don't seem to have this problem...it's isolated to the US. I'm looking forward to my trip to Israel next month when I won't have to spell my name for anyone.