I have practiced in several countries overseas... It is possible to work as an RN--- but even in the US, your nursing license is not automatically recognized in every state. You have to apply to the state's board of nursing before you can practice in that state (and many states have reciprocal or compact agreements where they recognize licensure from other states).
Likewise, overseas you must apply to the country's ministry of health, or whichever body governs nursing licensure. It is typically a time consuming and difficult process to complete on your own. The best option is if you are working for an international organization which already has a memorandum of understanding with the government. The organization accepts the responsibility of verifying your credentials and you are allowed to practice in that country as an employee of that organization. This is how many humanitarian aid organizations operate. My guess is that you would need US nursing experience before heading overseas.