The NHA's proposal was never adopted by Congress, but the idea of a national highway system lived on. A "Good Roads Movement" had actually begun in the 1870's, long before automobiles needed them. Bicyclists were behind that idea.
You can read about the U.S.'s national highway system here and the country's numbered roads system here.
Charles Henry Davis [1865-1951]
Source: U.S. Federal Highway Administration