If I overstay my visa in the US.

You will trigger a bar to future admission depending upon how long you overstay your authorized stay. The bar is triggered once you overstay by more than 180 days. Unlawful presence of more than 180 daysbut less than a year triggers a three year bar. Unlawful presence of a year or more triggers a ten year bar. There are additional bars to admission if you are removed by the U.S. Government. You can read more at http://myattorneyusa.com/unlawful-presence-in-the-united-states.