How did the national interest shape the policies related to regional commerce in the american system

Regional commerce policies are shaped as synecdoche by national interest. Each region is not necessarily a representative piece of the whole. Whereas regional interest may be varied, changing from region to region, broader scope national interest is more homogeneous, taking into account a majority of the larger group and eliminating outliers. Thus national interest shapes policies in a way that keeps regions accountable to a set of rules that keeps them relatively homogeneous across different regions.