A better solution would be to "re-model" the data.
The Date table has values for both dates and countries - split them into separate tables either using Power Query / M or use the DAX language in the data model itself.
Using DAX select the "Modeling" tab and press "New Table" button. Write the following formula:
Dates = VALUES( 'Date'[Date] )
Press "New Table" button once more and write:
Countries = VALUES( 'Date'[Country] )
In the resulting data model hide the original 'Date' table by right-clicking its name in the right-most pane and choose "Hide". Then create relationships between each of the new tables to your fact-tables 'Rev' and Traffic'.
Delete ANY relationship to the original 'Date' table.
You should end up with a data model similar to this:
You can then filter the data in the report on 'Dates'[Date] and/or 'Countries'[Country].
If the card visual used in the report still shows a (Blank) its because the combination of filters on the 'Dates' and 'Countries' does not exist.
The model above assumes that ALL valid combination of dates and countries are found in the original 'Date' table. Otherwise you might end up with "orphaned records" in either 'Rev' or 'Traffic' table - thats a record where the date or country in the table is not present in the calculated tables 'Dates' or 'Countries'.
Solving orphaned records is a slightly more complex solution - so I won't go into details here.