How to interact with the US Government and your Representatives in Congress
The US State Department Bureau of Consular Affairs working through US Embassies and Consulates around the world is your interface with US Government services when living abroad.
The Bureau sets guidelines and directs the Consulates for handling matters such as passport issuance and renewal, reports of births, deaths and marriages of US citizens, aiding destitute travelers, and issuing visas for foreign visitors to the US. To get an idea of the services offered by the Consulates, see this State Department webpage: travel.state.gov
If you want to contact your Member of Congress you can write to them directly or communicate to them via their individual website page. Find out who represents you using Contacting the Congress or BeBusinessed. To send a message on a Representative's website you need to use your last known residential address (even if you no longer have any ties to that address) in your Representative's district/state.