Where can I get data on transaction decline rate for each country for US transactions

One of my friends is considering to get an ISO/MSP in a country other than US but with majority of his clients’ transactions will be from US consumers. He wants to know if a non-US bank ISO/MSP will have any impact on the transaction decline rate for transactions coming from US customers. And if yes, then he is interested in knownig the country specific transaction decline rate world-wide. Kindly help. Thanks.