I recently moved from Sweden to the US. Now that my bank is here in the US, I switched my Apple account over to the US region.
Doing so made everything under “Purchases” and “Updates” disappear in the Mac App Store. After a long frustrating email exchange I was told by the App Store support that apps are tied to a region, so if you have downloaded an app in one region it’s forever tied to that region. Their message was: You have to keep your account in the Swedish region to receive updates. Note that this applies even to free stuff like Twitter!