The map border tells the software how large to make the map. Draw a new map border, delete the old map border, and then extend the background to the new map border.
The map border is on sheet and layer map border.
Not on the political border/political sheet/layers.
To make sure you only delete the old map border, hide and freeze everything else.
Some thoughts regarding you key size problem: The required size of the key depends on the resolution and final screen/print size you plan to use. The forum, for example only allows for relatively small resolutions. So, if a key shall be readable in a picture for the forum, the key needs to be big. If you use the same picture in a much higher resolution, you could use a smaller key and the fond would still be readable.
Comments
The map border is on sheet and layer map border.
Not on the political border/political sheet/layers.
To make sure you only delete the old map border, hide and freeze everything else.
N4
N4
(Edit: I found it. Was easier than I thought. Just used Draw Like command and drew the box. Duhhh)
Some thoughts regarding you key size problem: The required size of the key depends on the resolution and final screen/print size you plan to use. The forum, for example only allows for relatively small resolutions. So, if a key shall be readable in a picture for the forum, the key needs to be big. If you use the same picture in a much higher resolution, you could use a smaller key and the fond would still be readable.