This may not be what your looking for, but I made an attempt using the
Map Options: Data Layer component.
I picked a random Layer, like Population,
and then used a Custom Color palette
to make the background of all states black.
<color-palette name="Black" type="ordered-sequential" >
It then shows states that don't have data,
but it also blackens the bodies of water, and gives
a tinge around the outer borders.
203317map.twbx 9.7 KB
You have a couple things working against you here. If you create a formula to return a zero for states with no values or even if you padded the data, when you filter the state will disappear completely. It looks like you have washed out the map completely so you can't use a map layer to draw the borders.
The best you could do in this case is instead of washing the map out, just uncheck all the map layers. Then turn on a data layer by state and color it something like gray. I used the population by State in the example below. It will fill the States that are filtered or missing with gray hues. They do not interact with tool tips. The only question you might have to answer is why the different color gray.
Here is a version with the filled map on postal code, but you can see better what would be behind your marks.
map.twbx 422.5 KB
Thank you for the replies Adam. I will give this a try and let you know how it works for us.
Any suggestions for how to achieve this on Tableau Public? Not sure if Tableau Public users have the ability to change "My Tableau Repository".
Thanks for any help or insight!