I think that it would be D
They believed every human had rights and deserved to live
The answer is Oregon. This is solidified through the treaty called the Treaty of Oregon. In this treaty, the US and the British government had created a boundary to stop states to fight over their territories. The treaty had stated that Oregon county is a joint territory between the US and the British government.
Lewis and Clark traveled up the Mississippi River that compromises the Louisiana Purchase to reach the Bitterroot Mountains.
Most countries dont need "justification" for joining a war, typically the only justification is a decision backing up allies, and under this definition, the US was justified, Japan had also initiated aggression againts the US, giving the US an incentive to join the war, so yes, its likely that they were justified in joining the war, for several reasons
