Trump tells Puerto Rico after a few weeks that the Military, FEMA and first responders can't stay there forever. Really?

There are  199,435 American troops in 177 countries around the world. Following are the top 20.

Japan 39,345
Germany  34,805
S. Korea 23,468
Italy 12,102
Afghanistan 9294
UK 8479
Kuwait  6296
Iraq 5540
Bahrain 5504
Guam 3831
Spain 3256
Qatar  2976
Turkey 2234
Djibouti 1961
Jordan 1759
United Arab Emirates 1079
Belgium 845
Cuba 806
Romania 667
Greece 407

What are they doing there? Are they going to be there FOREVER?