House Sparrows are a world-wide invasive species. These Old World sparrows were first introduced to New York in 1851 and 1852. With their preference human-altered habitat, the species quickly spread across eastern North America. These introductions were augmented by subsequent releases in the western United States.
Although House Sparrows remain common, I do not think I see as many as in my youth. Breeding Bird Surveys demonstrate a general population decline across the United States and Canada—a decline of about 2.5% per year. European numbers are also going down. Hypotheses for these drops in numbers include increased use of pesticides, which reduce insect numbers that adults feed to their young, and efficient farming practices that result in both less grain spillage and fewer weed seeds that used to support huge sparrow populations (Lowther and Cink 2000).