Complex sentence: The US declared war, the War of 1812, and invaded Canadian territory, in response Britain invaded the US but the pre-war boundaries were reaffirmed by the 1814 Treaty of Ghent, ensuring Canada's future would be separate from that of the United States.
Split into simpler sentences: The US declared war, the War of 1812, and invaded Canadian territory. In response Britain invaded the US, but the pre-war boundaries were reaffirmed by the 1814 Treaty of Ghent, ensuring Canada's future would be separate from that of the United States.