Assisting other countries experiencing a crisis

In recent years, the American armed forces have been called on to perform duties that are more humanitarian than militaristic, providing support after the Fukushima disaster, in addition to funds for drought victims in Ethiopia, COVID-19 vaccinations to countries who could not afford them, Ebola patients in West Africa, and earthquake victims in Nepal. Do we have an obligation to assist other countries experiencing a crisis, or should that be left to private relief agencies such as the Red Cross?