The only reason Transdniesteria is not recognized as a country internationally is because of political discrimination. There is a history of this: From 1917 to 1933, the Soviet Union was unrecognized by the United States.
This was an attempt by Washington to isolate the largest country in the world (by landmass). Today, Washington is doing the same with Transdniestria. Transdniestria is not recognized because of a "Washington-consensus" which, since 1990, has selectively only recognized those states which are favorable to U.S. hegemony in the world.