The imperialist nations were responsible for creating a series of problems in the dominated countries. The so-called "civilizing project" defended by supporters of neo-colonialism ended up bringing changes and problems that have not ended yet today. According to several scholars on the subject, African and Asian countries are still experiencing the terrible effects of the control developed in the 19th century.
The world was divided and submitted to the great European powers and the United States. There were no more territories without an owner and the great powers fought among themselves in an attempt to expand their areas of economic and political domination, and this caused the WWI. One of the great influences of the first war was the Chinese revolution, that was the revolutionary process responsible for the transformation of China into a communist nation.
With all this division between capitalism and communism countries there was the outbreak of the WWII.
When American English is better, it's better because it's easier to imitate or learn if you're learning English. Our accents are more flexible than the British ones. ..
Hey the answer is trench warfare. presuming you're talking about when they fought in trenches across no mans land. hope this helps, have an amazing day :)