it fell apart because the government changed.
Yugoslavia
Yugoslavia and the USSR (Soviet Union)
Yugoslavia
Croatia didn't fell apart. But Yugoslavia fell apart and one of the countries is Croatia.
Yugoslavia was a country in Southeast Europe that existed from 1918 until the early 1990s, when it began to break apart into several independent nations due to ethnic tensions and political conflicts. Today, the former territory of Yugoslavia comprises several countries: Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, North Macedonia, and Serbia. Each of these nations has its own distinct identity and government, having emerged from the dissolution of Yugoslavia.
Czechoslovakia, Yugoslavia, & USSR.
Yugoslavia split apart into several republics in the 1990s. These republics included Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, Macedonia, and later Kosovo.
The Soviet Union and Yugoslavia are such countries.
Croatia didn't split
The correct spelling is collapse (to fall down or apart).
All the treaties"fell apart" because the US government failed to honor them or to enforce them.