There are some significant U.S. embassies that are influential because they are in major cities of powerful countries, like the ones in Moscow and Beijing. As of 2015, other U.S. embassies like those in Brasilia and Baghdad are just as influential as they develop into strategic outposts through which the U.S. Government exercises and strengthens American interests.
Russia and China are large world powers that have economic, cultural and militarist tentacles stretched throughout the world. For these reasons, it would be irresponsible for the United States to not represent itself in either place. Another obviously influential U.S. embassy is the one in Tel Aviv, Israel. As the most openly democratic nation in the Middle East, Israel is an important ally of the United States.
Two other U.S. embassies that are remarkably influential are located in Brasilia, Brazil, and Baghdad, Iraq. Brazil, a country of 204 million people and the only trillion-dollar economy in South America, is a mostly peaceful Republic from which the United States can advance its influence in Latin America. The U.S. Embassy in Baghdad, Iraq, has been shrouded in mystery. As of 2015, it's the largest embassy in the world. It cost $750 million to build and employs 15,000 people, even though U.S. troops have left Iraq.