There are multiple options for organizing and deploying your decision project. Here is the one with one decision model for all countries deployed as one Lambda.
Your project may look similar to any sample project like VacationDays. A possible structure of your rules repository:
Your MainDecision.xls may start with running some common rules (like InputValidationRules.xls) that will set the variable “Input Validation Result”. If Input Validation Result is SUCCESS then it will execute CommonRules and SelectCountryRules (a multi-hit decision table). We assume that Country is your input variable. For different countries, you use ActionExecute to invoke the proper rule like RulesCountry1. This schema may work fine at least for the start.
If you find out that some rules require too much data going through the network, you may create a separate country-specific project and deploy it as a separate Lambda. Then you may invoke this Lambda from the same table SelectCountryRules just using already mentioned Service Orchestration. Contact us if you have specific questions and we will help.