Biggest "what ifs" in history?

[RagaZ]

What if Gavrilo Princip hadnt shot Franz Ferdinand?

What if Al Gore had won the 2000 Elections instead of Bush?

[StephHamann]

What If a giant asteroid had not wiped out the Dinosaurs?

[LexiKhan]

What if the Moors managed to hold on to their territories in the Iberian Peninsula?
Would the American Continent still be rolled over by other western countries or maybe China?
Would the Aztecs colonize north america eventually?
Would South America be one huge Incan Empire?

[fiddy]

What if american trash did not intervene in WW1 and WW2. Europe would be so much better.