Although El Salvador is a small country in Central and South America, it has a population of 6.5 million. These 6.5 million people will be potential users of Bitcoin. Bitcoin is definitely more beneficial than exploitable.
Though the population of El Salvador might be small as you rightly said however there might be few individuals in that country that might be very rich and whose investment in Bitcoin might trigger price change coupled with other fellow country people, in a nut shell the numbers of users of bitcoin will continue to grow if the unbanked populace also utilized saving or storing their bitcoin in their respective wallets for easier P2P transaction and more so there is the tendency of other south American countries adopting bitcoin after El Salvador.