For decades the U.S. Army Special Forces spent much (often most) of their time training foreign troops but since September 11, 2001 the Special Forces and the rest of SOCOM (Special Operations Command) has been in great demand to do combat missions. So soldiers and marines have stepped in and taken their place.
It was soon discovered that as good as the Special Forces were at training foreign troops, many of these foreign armed forces now prefer American soldiers and marines. This began when some U.S. officers, responsible for assisting in the training of military forces in Third World countries began declining when Special Operations Forces (SOF) personnel were offered. Publicly, the reasons were usually couched in terms that suggest the SOF people were needed elsewhere, which is certainly true, given ongoing operations in Afghanistan, Iraq, and so on. But privately some of the advisory personnel cite the fact that SOF personnel usually bring with them all sorts of specialized equipment that the host country will never be able to afford. Moreover, the capabilities for which SOF trainers provide training for are often much too sophisticated for local, and usually poorly educated, troops to absorb. An additional objection is that the nature of the way in which SOF operates is just too "undisciplined" for Third World forces. Apparently when asked, experienced advisors will ask for American marines rather than Special Forces. The marines have been helping out with the foreign troops training since the war on terror began, and the more basic and down-to-earth approach of the marines has been more attractive to many nations. Soon the demand was so great that the U.S. began sending soldiers and these proved just as capable.
American soldiers in particular have been heavily involved in training African troops on the best methods for hunting and killing the Islamic terrorists. Many of these American troops have practical experience and their African trainees appreciate that. Language skills are not as important as combat experience. There are plenty of English speakers in most African armed forces and a lot of instruction can be given with no knowledge of the local language, just a knack for showing how it’s done.
The SOF are still very good at organizing and training irregulars and educating local special operations troops and counter-terrorism forces. But when it comes to turning a bunch of civilians into disciplined troops, the soldiers and marines have an edge.