So this varies very much depending on where you are from in the US. While there is a good portion of Americans who must truly think that cars just have to stop when they step onto the road (mostly New Yorkers), there are many who wait for the light to be green before they cross. Although this action might be fine in New York, it could get someone killed in another country.
Cars will usually stop for someone who is crossing the street, as they don't want to hit anyone, but they are not as accustomed to it as in other places.