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In this case, the correct answer to why John C. Calhoun and others first advocated for an "American System" is:
1. It provided a plan for a more economically independent America.
The "American System" aimed to promote economic independence for the United States by implementing policies such as protective tariffs to support American industries, a national bank to regulate currency and credit, and internal improvements like roads and canals to facilitate transportation and trade within the country.
By focusing on economic self-sufficiency and boosting domestic industry, proponents of the "American System" believed it would strengthen the nation's economy and reduce dependence on foreign goods, thus enhancing America's overall economic stability and growth.