After the 1812 war, Americans saw themselves “not as an independent nation, but as a player on the world stage.” What does John Green mean by this? How did this war change the way Americans viewed themselves and their country?

Read lots. Read carefully.

https://www.google.com/search?q=how+did+war+of+1812+change+americans+view+of+themselves&oq=how+did+war+of+1812+change+americans+view+of+themselves&aqs=chrome..69i57.14721j0j7&sourceid=chrome&ie=UTF-8