Can I Buy a WoW Token in one Realm and Sell it in another Realm?
According to Blizzard, when it comes to the WoW Token usage, you only need to pay attention to your account's region. In other words, if you obtain an EU WoW Token, it only works inside that part of the planet. Similarly, the US WoW Token becomes region-locked to those Realms or servers.
At the moment, you could obtain a new WoW Token in Realms that belong in regions such as the Americas, Oceania, Europe, China, Korea, and Taiwan. Again, even if it looks kind of "silly" to have these kinds of limitations, it aids to protect your purchase. You will only see the possibilities of the currency/game time you'll get when you look to obtain some WoW Tokens.