Explain ONE historical situation in the period after 1900 in which a

new, less diverse state replaced an old, more diverse empire.

The Habsburg empire

Explanation:

Before the first world war the Habsburg empire encompassed not just Austria and Hungary, but Bohemia, Slovakia, Slovenia, Croatia and large parts of Poland and Romania.

On the 28 June 1914 the Archduke Ferdinand of Habsburg was killed in Sarajevo; this led to the first world war in which the Habsburg empire lost its enormous empire. After the war new and less diversed nations were created from the old empire such as Austria, Hungary, Czechoslovakia and Yugoslavia. The latter proved to be too etnically diversed too. Austria and Hungary, although with a Romanian minority inside and a Hungarian minority in Romania, proved to be more stable.

idk you know what i mean hahahaha