Can't select club from different countries despite selecting them as playable

What is your game mode? This is an intended behaviour if you playing with Real World or Your World mode.

Hello, as mentioned above, what is your game mode?

If you playing with Real World or Your World mode this is working as intended. The user can only select teams from the Game Start Date nation. To avoid scenarios where the start date may precede the database date (particularly important in Real World mode)

We will make this visually clearer to the user when setting up a new game in a future update. 

I was indeed using Real World mode. Thanks for the clarification, and I agree some info during selection would be handy for new players coming across this behaviour