Lot of countries that gained independence in the 1800's were actually not able to survive on their own, or at least to not be very poor and in terrible position. The reason for this was that most of these countries did not had properly established economies, and everything prior to their independence was controlled from another country, but now that was all gone. Also, they were not industrialized, big portion of the natural resources were not used because there was no suitable equipment, nor there were proper means for developing a long range trade. So basically these countries were surviving on the good will and interest of the more powerful countries, such as the USA.