Carne de caballo - depends on the country
I know that Mexicans, some South Americans, some Europeans and others eat horsemeat, but in El Salvador it's generally not permitted to sell it in the marketplaces. There is little demand for it, and therefore the authorities don't really have the means to adequately check the slaughtered animals for possible diseases before the meat is sold.
I think that in some countries, especially within the Anglo societies as you mentioned, there is a cultural bias, or disdain, against eating horsemeat, despite the fact that it's just as nutruitonal as beef.