If it’s a an expected country code, answer the phone.
If it’s an unexpected country code, leave it alone.
Does this work somewhere? In Canada, spam calls are always my country code (which is shared with the US). Area code means little these days, too. Spammers will just spoof numbers.
Well it is a decent first level of defense. I usually get foreign country codes. But obviously don’t trust local numbers either. Let them introduce themselves (don’t introduce yourself) and ask if you can call them back in a minute. In the minute, check if the number is really who they claim to be. Then call the number if it matches and you are interested in the conversation.
If it’s a phone call, leave it alone. They’ll leave a message if it’s important.