Blizzard does this to prevent money laundering outside of country boundaries. That's why they 0 it out.
Honestly, you should keep an updated address if you want to utilize services. I update my address when I've moved at everything I care about
Post Office (mail forwarding)
Cell Phone company
...now just add Blizzard to that list.
Also, the region change may result in you not being able to utilize the US-based AH. This is also to prevent scammers.
I'm glad they have these policies and audits. Sorry to say, but you should have taken more care, OP.
While you have a point to a degree, it in no way takes away from the OP's main point which is, if this was an issue they should have stopped him when trying to DEPOSIT not from SPENDING, what they did is plain wrong, and needs to be corrected.