How does 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.