Nikons product line maintains its nomenclature across ALL regions. The poster aboves confusion comes from the fact that the XT/XTi, XSi are ACTUALLY the 300D, 350D, etc. etc. I also believe the classification of products is maintained on the prosumner line, but why there are two names for these entry level cameras in US territories is beyond me.
Why would they? Maintaining consistency allows them to have a streamlined product line that is easily traceable.
The idea is that calling something a memorable name makes it more appealing to consumers I guess-- and they have a point on that front in that the Rebels stand out from the alphanumeric morass that is modern digital photography. The use of the term Rebel dates back to the early '90s when Canon brought out the first "consumer" grade AF SLR under that name in the US.
It's dumb, but nowhere near as dumb as both companies weird numbering issues: Canon came out with the D30 and D60 before suddenly reversing course and starting with the 10D. Despite all this silliness, for their pro lines the numbers themselves are what represent the products, so they don't even get new product numbers, just iteration indicators (which is NOT what they did for film cameras, instead adding new letters after the 1, which is even more confusing). Not to mention that the 1D vs. 1Ds bit is even more baffling.
Nikon brought out the D50 and D70, before coming out with the D40 and D60, yet neither is really a successor to the D50. At the same time, what are they going to call the successor to the D90? They already had a D100, and it will break their two digit naming scheme. On the pro end, they broke their tradition of having an 'h' and 'x' body, though that's not as big of a deal.
Maybe we'd be better off if every camera just had a neat name like they do with cars.
"oh check out my sweet new Canon Viper!"
"oh yeah, well my Nikon Vanquish is way cooler"