Your choice of job is not just confined to the 50 States of the US. The Diplomatic Service and the Military are other options which could take you almost anywhere in the world.
The map above merely highlights those territories with some connection to the US. Some may be all-but-independent while others may be locations for military bases or politically-sensitive areas.
The map is dominated by Pacific-based territories for obvious reasons. But it's not just those we have highlighted that have a strategic value. This is because the world we live in is still in a state of turmoil as dominating countries are seeking to protect their interests. Then there is the phenomenon of emerging ideologies which are redrawing the boundaries of some countries.
The point is that working overseas can be divided into two main areas - those with civil/political interests, and those with military interests.
If you do decide to work overseas for the State, always consider the implications of doing so, as being located in one country does not mean that will be your permanent place of work.