2 Domain and 1 website

Hi everyone i have a website on NZ domain. And i want if someone opens a website from USA or from any other country website domain will automatically change to ( .com ) domain. And the current will also change to USD when someone opens a website other than New Zealand.

-I want to manage both domain from one CMS.
-All products will be control from one CMS.
-I need another separate email address for (.com)