what event three weeks after the march on washington showed americans that change was needed?

The Klu Klux Klan bombed an “African American Baptist church in Birmingham”, Alabama, on September 15th, 1963.

Explanation:

On the morning of 15th September 1963, America suffered the biggest loss in his history. On that morning, the members of Klu Klux Klan had planned an attack in America. The “16th Street Baptist” “Church in Birmingham”, “Alabama”, a place for and African American gathering where they together worked for civil rights and held campaigns went through a bomb attack. That shocking attack killed four girls and injured hundreds of people resulting into casualties. This event showed Americans that change was needed.

The Birmingham church bombing.

explanation: we can only guess at how our actions may be perceived in the future. doing something really big like killing lots of people, saving lots of people, affecting the lives of lots of people is a sure fire way of being remembered in historical records. we can also make a difference in the history records by being a small influence on something bigger, whether that is as a civil servant, scientist or artist.

of course you could argue that we all affect history just as tiny cogs in a   bigger machine.

if you mean how do people influence our opinions of things which have already happened, then simply by writing a book which looks at things form a different perspective and trying to convince people that this perspective is more accurate or truthful. people do it all the time i.e. richard the third was a terrible or was he? plenty would disagree, it's just that their views aren't the most widely known.n:

giant bugs

explanation: