Regional trade and international trade in a big country can both replace and promote each other, leading to enhanced nation competitiveness. Different regions within a country have varying resources, leading to inevitable trade but uncertain patterns. International trade can boost domestic regional trade, leading to economies of scale and lower production costs. This increased specialization and productivity can improve product competitiveness in international markets, ultimately benefiting the nation's competitiveness. The example of the United States shows how regional trade played a crucial role in enhancing nation competitiveness post-independence.