1900's: Theodore Roosevelt
1910's: Woodrow Wilson/Kaiser Wilhelm II (tie)
1920's: Eh... the 20s were boring. Coolidge, I suppose, those he's really just representative of them.
1930's: Franklin D. Roosevelt/Adolf Hitler (tie)
1940's: Winston Churchill
1950's: Nikita Khrushchev
1960's: Martin Luther King Jr.
1970's: Richard Nixon
1980's: Ronald Reagan/Mikhail Gorbachev (tie)
1990's: This is difficult... the computer or the internet or something, if that's allowed
2000's: George W. Bush
7 Presidents. Interesting.
Shows a lot about you: namely, Amerocentrism.
For a few of the choices, sure. Theodore Roosevelt is the most obvious, but there isn't really anyone in the aughts that impacted the entire world, and Roosevelt was in some ways instrumental in beginning what would be the "American century." Woodrow Wilson, FDR, Reagan, and Bush all undoubtedly had long term effects on the international political landscape.
