Geography & A Little Math
"P" + a country that uses the ruble as its currency = this historic German realm
Central U.S. state + "polis" = this capital city of that same state
Indianapolis
A West African country + "IA" = this other West African country
Nigeria
"Ar" + a central U.S. state = this other central U.S. state
Arkansas
"As" + a Middle Eastern country = this ancient empire
Assyria