Using System Manager public parameters a quick CLI one liner for checking if an AWS service is available in a region:

aws ssm get-parameters-by-path \
--path /aws/service/global-infrastructure/services/[SERVICE]/regions/[REGION] \
--output text

As an example, checking if Athena is available in ap-northeast-3:

aws ssm get-parameters-by-path --path /aws/service/global-infrastructure/services/athena/regions/ap-northeast-3 --output text

An empty result indicates the service is not available. The list of service names can be retrieved as below (from the documentation linked above):

aws ssm get-parameters-by-path --path /aws/service/global-infrastructure/services --query 'Parameters[].Name | sort(@)'

Similarly the list of regions can be found using:

aws ssm get-parameters-by-path --path /aws/service/global-infrastructure/regions --query 'Parameters[].Name'