If I was prevented from ever being born, how much of a difference would that make globally?

That is a question for which there is no direct answer. Just because you are a regular "joe" does not mean that somewhere in the future you may not be. If Adolf Hitler had been accepted into art school, World War II may have never happened. If the Khan's had not come to power in Mongolia, the Huns may have never been forced westward, and the Western Roman Empire may never have fallen. If a bunch of nobodies had no problem with a tax on tea, the American Revolution may never have happened. If there was never an oil embargo placed on the Empire of Japan by the United States, Pearl Harbor never happens. If a lowly Union courier fails to find the battle plans of General Lee, which were accidentally dropped by a Confederate soldier, the Union may not win the Civil War. Whether famous, infamous, or just a regular "joe", one never knows what the future holds and how that will affect the unfolding of human events. There is a cell phone commercial which shows it perfectly. Thanks to the ability of some regular guys app, he is able to change his train ticket so he can meet up with a woman he see through the window. This leads to the birth of a future president. The butterfly effect is a very powerful thing, which can alter society and culture in very dramatic ways from just the simplest of actions. Gene Roddenberry had a simple idea pf producing a television show about human travel through space, and they had all these cool gadgets. One was a communication device that they flipped open and spoke to each other with. Now we are calling each other on cell phones. All who are famous or important were at one time regular "joes" who, through the providence of happenstance were in the right place at the right time. Any small deviation in the events leading up to that happenstance, and they remain regular "joes". So never underestimate the power of the butterfly effect.