Complex sentence: The border remained the same after the war and was demilitarized, as were the Great Lakes, furthermore the British no longer aided Indian attacks on American territory, and the United States never again attempted to invade Canada.
Split into simpler sentences: The border remained the same after the war and was demilitarized, as were the Great Lakes. Furthermore, the British ceased aiding Indian attacks on American territory, and the United States never again attempted to invade Canada.