Well, I had the same issue of X5 imported from Japan. The connected drive system didnt work in NZ (New Zealand). When you try to download then register in My BMW app and after you insert your VIN number, the operation fails with an error saying that moving car country is not possible.
I have resolved this issue, inspired by what some people said here, however, things are bit more tricky now, since BMW changed their system and changed the URLs for pages. and now once you try to register, they detect your country from your IP address. So, there's no basic way for you to go to BMW web-site in Japan and try to register there (they will at some point redirect you to NZ portal [which can be seen in the URL "Country=nz"]).
So, I used a VPN to change my IP address to one in Japan, then I registered in BMW web-site (which is by default will be the Japan one), and used a new Email.
Then everything will work, you will register in JP BMW web-site, then you go to "My vehicles" section and click on "add vehicle" (of course everything in Japanese). Then you add the VIN, and they will send a code to the car. You go the car then, open "Connected Drive" -> Messages. and get the code from a message they send to you (in my case it needed 3 minutes to arrive after turning on the car and waiting on "Messages" page. Get the code and put in it. Then Done.
After that download My BMW app from scratch (remove it, if you had one before), and login using the email/pass you used to signup. Done
Working 100%
