No. As a matter of fact, the US backed out of international affairs after WW1 by withdrawing from the League of Nations. It did become a world power after WW2
Yes, Japan was on the Allied side in WWI, they captured several German colonies in th Pacific, and sent a fleet of ships to aid the allies in the mediteranean.
The First World War was important because so many people risked their lives to save our country, Britain. If those brave people didn't risk their lives, our country wouldn't be as it is today. Our...