How to make the economy of a developed country develop into a high-speed again is a problem that has puzzled thousands of economists for many years. In order to solve the problem, this paper establishes a new theory named "the theory of national economic development saturation". Based on this theory and take America as an example, this paper make a plan that can be used to make American economy developing rapidly and make America strong again: The first is a change, changing America into a developing county, to produce huge demands for investment and consumption; The second is policy innovation, to meet these demands; The third is action, constructing a number of large national projects, as the means of acquiring this great wealth. These projects are named "High-speed Railways add Super Cities Network Plan" (or HRSCNP). This huge plan would take America into new era of the annual economic growth of 7% or doubling the economic aggregate in 10 years, and add millions of jobs not only without losing money but also bring great profits. It might change the history of America and the world.