All Soviet-bloc countries with the exception of Romania boycott the US Olympics to retaliate for the US boycott of the 1980 Olympic games in Moscow.
Citation:
Editors. "Moscow pulls out of US Olympics".
The Literary Encyclopedia. First published 01 February 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=3801, accessed 24 May 2013.]