What are some ultranationalistic empires that lost their culture and religon through their expansion...like coverting

Answer 1

One early Egyptian pharoah (emperor):
http://www.google.com/search?q=amenhotep+iv+akhenaten&ie=utf-8&oe=utf-8&aq=t&client=firefox-a&rlz=1R1GGGL_en___US357

The Roman Empire

Alexander the Great's empire

Genghis Khan's conquered territories

As each got larger and larger, the central government had to depend more and more on the conquered governments to "mind the store." Needless to say, that can't go on very long before collapse.