Apple store credit, can't change my region!

i bought a few 50 dollar cards back when i was at USA. I have been happily using those credits and buying apps from the US store. Now i have 4.78$ left and i want to change my region and buy from my onw countries store, because there is less than 5 bucks left. I can't change the region because that 4.78$ cant just disappear a wanrning thing pops-up. What can i do? I dont care about that 5 bucks. I just want to be able to buy paid apps and change my region from the US store.