If you are sure that State HQ is used for AMER region while Country HQ is used for EMEA region, you could replace State HQ by Country HQ for those regions in the formula field.
But if you want to make it more flexible, i.e. depending on State_HQ being filled or not, then there are other solutions indeed.
You could e.g. replace State_HQ__c
by BLANKVALUE(State_HQ__c, Country_HQ__c)
everywhere you use it, and remove the one at the beginning where you check for ISBLANK
.
BLANKVALUE determines if an expression has a value and returns a substitute expression if it doesn’t.
https://help.salesforce.com/s/articleView?id=sf.customize_functions_blankvalue.htm&type=5
You might hit formule field limits, though, because it's quite a large formula already. If that happens, you might need to explore other options.
Example:
instead of
IF(ISBLANK(State_HQ__c), "",
IF(CONTAINS("Nunavut:Manitoba:Ontario:Quebec:Québec:New Brunswick:Nova Scotia:Newfoundland and Labrador", State_HQ__c ), "AMER - Canada East",
IF(CONTAINS("California:CA", State_HQ__c ), "AMER - California",
do this:
IF(CONTAINS("Nunavut:Manitoba:Ontario:Quebec:Québec:New Brunswick:Nova Scotia:Newfoundland and Labrador", BLANKVALUE(State_HQ__c, Country_HQ__c)), "AMER - Canada East",
IF(CONTAINS("California:CA", BLANKVALUE(State_HQ__c, Country_HQ__c)), "AMER - California",
i.e.
- remove the first line (and don't forget to also remove one closing
parenthesis at the end of the formula)
- replace every other occurence of
State_HQ__c
by BLANKVALUE(State_HQ__c, Country_HQ__c)