Prohibition does not work, because people will always be able to sneak the illegal substances into the country somehow. And this causes problems, because it causes many conflicts and casualties between the government and the smugglers, but the government will never be able to stop the smuggling entirely.
Without Teddy Roosevelt's reformation, business would still have been able to cheat their workers into very low wages and bad working conditions. Another reason is that the acts and laws he passed bettered the quality of life for all people.
http://www.nobelprize.org/nobel_prizes/
Without the Zimmerman Telegram we probably would have stayed nuetral, because then we wouldn't have felt under pressure.
http://militaryhistory.about.com/od/
I think that WW1 was very split between the Central and Allied powers, because we had stronger ties with Great Britain, but most of the population in America was German. I think the reason we joined the Allied powers is that the Germans were stopping our trading to Briatain and other countries, and also all the threats they put on the U.S.