Serbia and Montenegro remained joined in Yugoslavia.
The good ole USA
Latvia, Lithuania and Estonia.
It isn't as simple as Russia changing its name. No single nation "became the Union of Soviet Socialist Republics" And it wasn't in 1917. In 1922, Russia, Ukraine, Belorussia and the Transcaucasus Federation (a union of Georgia, Armenia and Azerbaijan) joined together to form the USSR by entering into the Treaty of the Soviet Union. As time went on other nearby republics either joined or were absorbed into the USSR.
No. Yugoslavia began to break up in the 1990s. Some new countries that formed as a result of that breakup joined the EU in 2004 and later than that. Some of the countries that were part of Yugoslavia are not members of the EU, but may join in the future.
Yugoslavia
Serbia didn't drop out of World war I. After having initial success in the battles of Drina, Kolubara and Cer ( which were first allied victories in the war) against Austro-Hungarian troops, Germany joined the invasion. Serbian army was then forced to retreat through Albania to Greece, where it joined its allies and reopened the Solun front. Serbia came out of the war victorious.
No country joined in 1954. Greece and Turkey joined in 1952 and West Germany joined in 1955.
Romania was one of the Axis Powers in WW2. Meaning, no they joined him instead.
The Founding Members (1949): United States of America, United Kingdom, France, Italy, Canada, Netherlands, Belgium, Portugal, Norway, Denmark, Iceland and Luxembourg. Joined in 1952: Greece and Turkey Joined in 1955: Germany Joined in 1982: Spain Joined in 1999: Czech Republic, Hungary and Poland (all were members of the former rival Warsaw Pact) Joined in 2004: Bulgaria, Romania, Slovakia, Slovenia, Estonia, Lithuania and Latvia. (all were previously Warsaw Pact - except Slovenia which was previously part of neutral Yugoslavia) Joined in 2009: Croatia (former Yugoslavia) and Albania (former Warsaw Pact)
It did so in 1777 and remained one until it joined the Union in 1791.
U.S.S.R stands for the Union of Soviet Socialist Republics, which was made by Russia in 1922 when it joined the Ukraine, Belorussia and the Transcaucasian Republic (Armenia, Georgia and Azerbaijan). Over the next number of years, the USSR absorbed other republics into it.
No country joined the European Union in October 2007. Two countries did join in 2007, Bulgaria and Romania, but they both joined on the 1st of January 2007.