Even in rural areas there is a lot of extra lighting. The net effect is that you cannot see much of the night sky. Even if you block out the light, the combined effort of all the lights will cause the sky to have a slight grayish tone that shows up in photographs. The more lights around you, the brighter that background, the more stars obscured. Depending on where you live or where you setup your camera to take pictures of the sky, the light pollution will have varying effects on your work.
Light pollution is worst in the city and near cities.
In these locations you will be lucky to catch a glimpse of all but the brightest stars. To take good pictures of the night sky with a camera you need to get away from the city lights and out deep in the country. Highways and places where people drive by should be avoided as well. The lights of cars can ruin a photograph if it arrives at the wrong time. Another form of traffic to be concerned about in many areas of the world is in the air.