The U.S. government is good at doing what it's not supposed to be doing – invading other countries without provocation, utilizing "soft power" in order to pull off regime change, enriching politically favored economic interests under the guise of promoting "democracy" – and very bad at doing what it really ought to be doing, i.e. protecting Americans from actual physical harm emanating from overseas.
Overthrowing "rogue" regimes? Check!
Protecting the American people from highly contagious diseases? Forget about it.
Over 300 U.S. troops have been sent to Liberia, the epicenter of the current Ebola outbreak, with 700 expected in the country by the end of October. As many as 4000 are projected to be part of the effort eventually, although officials maintain that this number is likely to be variable. Their purpose? According to this Associated Press report: