Perhaps brutal measures taken in WW II, such as mass bombing of cities, their justification, and were the results consistent with the justification.

Spanish Flu of 1918 … how come so many people died before the government figured out what was happening?

Perhaps the struggle to get the right to vote for women.

Perhaps figuring out about Typhoid Mary and the issue that she was in denial that she was a hazard to other people.

Perhaps how the early european colonists interacted with native indians & how come it was neccessary to do so much genocide.

Regime change has been done dozens of times in the last few centuries. Get an example of when it had long term benefit for both the people of the place where it happened, and the people who engineered it … maybe Puerto Rico. Get an example of when it had disasterous consequences for foth the people of the place where it happened, and the people who engineered it … maybe Germany making communism happen in Russia.

Obviously it is too soon to know what the results will be in recent cases like Iraq, but see if the evidence supports my premise that regime change at best has short term benefits, but almost always is a disaster for the people who engineered it.