Just trying to fill the background layer. What am I possibly doing wrong here?

[squatcobbler]

I have this crazy idea. I want my background layer to be white. 

I've tried selecting the layer and doing Edit->Fill with BG Layer

It doesn't fill all of it.

So I select all of it. Try the menu item again. No. Still doesn't fill the transparent part. 

I google. Aha! Shift-B and then choose "fill selection if necessary" or whatever.  Nothing works!!! A trivial task and it just doesn't work. 

I keep selecting all of the layer and it never fills. 

I've spent an hour just trying to fill a flat background layer with white, see attachments.  I'm sorry but this is absurd.

[rich2005]

Not too sure how you got to the layers you have, there is more than one way. However, look at your background layer and that dotted line. That is the layer boundary and is the reason you cannot paint / fill outside it.

To fix it, with the background layer active (as shown on your shots) apply Layer -> Layer to image size That moves that right side boundary. If the background layer has no transparency (alpha channel) it will fill with the current BG colour. If the layer has an alpha channel use the bucket fill as normal.

40 second demo: https://i.imgur.com/CtBauI9.mp4