The similarity between the single and double UPU international postal cards may have been responsible for the unauthorized use of this single international card from the Soviet Union to the United States. Only the reply-half of a double card should have been valid into the U.S. from abroad.
Several republics of the Soviet Union were brand new members of the UPU when this card was used in February of 1948, having been admitted only the previous year.
The "World Tourists" organization sounds like a communist-sponsored one, since I don't imagine there were a lot of "tourist" citizens in 1948. One of these days, I'll have to get this one translated for more clues.
The card has a nice transit marking from Byelorussia, possibly suggesting that it came across the atlantic ocean en-route to the U.S.
Place mouse on image to see the reverse side of the card.