Problem using DLC from another region

The problem with US DLC not working with a non US game is due to the game TitleID being different. US games have a TitleID starting with BLUS{5 numbers} and EU has BLES{5 numbers}. If you have for instance an EU game it stores gamedata and savegames in a folder starting with BLES00000 for instance. And the DLC will try to install under BLUS00000 so your game cannot see the DLC due to being installed in a different location. There is no way to fix this without getting a copy from the appropriate region. On the spine of the game boxes on the bottom is the TitleID for that copy.

List of most used titleID prefixes: BCUS - sony REGION 1 game BLUS- 3rd party REGION 1 game

BCES - sony REGION 2 or 4 game BLES- 3rd party REGION 2 or 4 game

BCAS - sony REGION 3 game BLAS - sony REGION 3 game

Make sure you get a copy from region 1 if you have US DLC.