Population density

What would the population of the United States be, if it were as densely populated as India?  I was under the impression that India's population density is only slightly greater than that of the U.S.  This assumption is wrong.

The answer to the question is 4 billion people.  When will this happen?  The quick way to answer this question is to consider historical growth rates.  During the 20th century, the U.S. averaged 1.3% population growth per year.  At this rate, population would reach 4 billion by the year 2210. A lot can happen in 200 years to affect the actual growth rate.  That being said, the U.S. may reach a population of 1 billion—the equivalent of the population density of Europe—by the year 2100 at a 1.3% growth rate.