Is there a way to detect collision with a background layer, without grabbing/using player coordinates to check for every single wall?

Not that I know of... I usually use the player coordinates and check the blocks around the player for colision.

well I simple way I do it is using bgget, ok lets say you have your player in the middle of the screen and your player is moved using the circle pad I would use this code. (brb)

so this would be used for overhead movement where the bg moves and player stays in place the x/y is the bg location.

maybe this helps but tell me what you think or if you have a question.

if no standard method exists, i would say make your own algorithm that acts as its own collision detection.