Map is not full screen in Google Earth Pro
Happened to me too, Its a graphics driver problem. It does not work on X.org nouveau graphics driver. More on it here. So you can uninstall the present version 7.3 and install 7.1 version from here.
I have nouveau graphics driver and Google Earth Pro 7.3.2.5776 (64-bit) on Ubuntu 18.04 LTS.
You can try to use LIBGL_ALWAYS_SOFTWARE environment variable like this:
LIBGL_ALWAYS_SOFTWARE=1 /opt/google/earth/pro/googleearth
But this is just for a little look, because it is terribly slow.