the country that forms the northern boundary of the United States is Canada :)
This is the boundary with Ukraine: mountains and the river Tisa.
The sea that forms the northern boundary of Africa is the Mediterranean Sea. The countries of Morocco, Algeria, Tunisia, Libya and Egypt border it.
red river
The Arctic Ocean
The sea that forms the northern boundary of Africa is the Mediterranean Sea. The countries of Morocco, Algeria, Tunisia, Libya and Egypt border it.
Most of the northern boundary is formed by the Alps. However, on the Iberian Peninsula, the Pyrenees form another northern border of Southern Europe.
Mediterranean Sea
The river Danube and the South Dobrogea.
The Mediterranean Sea is on the northern boundary of Africa.
The Putumayo river forms the northern boundary between Peru and Colombia.It is one of the tributaries of River Amazon. The name Putumayo means "gushing river".It is also know as Ica river.
Carpathian MountainsThe Carpathian Mountains.