This is a nice quiz. Just a suggestion, you can merge cells together to make it look a bit neater (this would be used for the Korean War cells) - go to Design Grid, change the design to Manual, go to the right and click Merge Cells > Down
You should pin your first comment the one saying 'This is my first quiz so if there is anything wrong with this quiz, just let me know'. Also you should choose a picture of the China flag from Wikipedia because the one from Pixabay looks a little weird. Otherwise this is actually a really good quiz even though it's your first quiz!