The two reasons:
- Britain intercepted the Zimmerman Telegram
- Germany resumed unrestricted submarine warfare
Context/detail:
Public outrage in the US against the Germans swept the nation following the sinking of the British ocean liner, <em>Lusitania</em> -- but that happened before 1917. When a German U-boat (submarine) sank the Lusitania in May, 1915, over 1,000 persons were killed, including more than 100 Americans. The passenger liner was targeted by the Germans because they suspected weapons were being shipped to Britain in the cargo hold of the ship.
Germany managed to stave off American entry into the war at the time by pledging to stop submarine attacks. But a couple years later they resumed such attacks, and there was also an intercepted telegram (the "Zimmerman Telegram") that showed Germany was trying to secure Mexico as an ally against the United States.
In 1917, the US declared war on Germany in response.
This is called the frustration of purpose. It's a doctrine about how cases would be solved if unforeseen circumstances were to occur. A modern example would be if you took a mortgage but an earthquake completely destroyed your house. Due to the frustration of purpose, you could have your mortgage canceled because you don't have a house that the mortgage was for, so you wouldn't have to pay for it any more.
Answer:
These terms may not have been the most appropriate because people, specifically Indians who discovered what we call America (we know them as American Indians/Native Americans). It was not a "New World" or "discovery" to anyone besides Christopher Columbus and his followers; people already knew about it. A term that may fit what he found better is "learning" or "exploration", but it is important to recognize that he did not find America himself.