Short answers, pulled from the story.
The United States embargo enacted in 1807 resulted in a static welfare loss estimated at 5% of the nation's GDP. This policy lasted from December 1807 to March 1809 and stands as one of the most severe peacetime interruptions of international trade in American history. It demonstrated that restricting imports can strangle the flow of goods and reduce national income.
Prime Minister Sir Robert Peel achieved the repeal of the Corn Laws in 1846 with the support of the Whigs. These laws had imposed tariffs on imported grain between 1815 and 1846 to protect the profits of landowners. The repeal marked a decisive turning point in global economic history by shifting the United Kingdom from a protectionist stance to one of free trade.
The Tariff Act of 1930 raised the average tariff on dutiable imports from approximately 40% to 47% and provoked international retaliation. This act reduced global trade and contributed to the severity of the Great Depression by limiting foreign access to U.S. dollars. The resentment generated by the act encouraged other countries to form discriminatory trading blocs and hindered global economic recovery.
U.S. economic growth during the late 19th century was driven more by abundant natural resources and openness to people and ideas than by high tariffs. The country experienced large-scale immigration, foreign capital, and imported technologies while remaining open in many respects. Economic growth occurred significantly in services such as railroads and telecommunications rather than solely in manufacturing.
The Opium Wars were fought between the United Kingdom and China over the right of British merchants to engage in the free trade of opium. These conflicts illustrate how trade disputes can escalate into armed conflict when goods cannot cross borders. The wars demonstrate the volatile intersection of economic policy, addiction, and military force.
Beginning in the 1940s, Argentina erected a system of almost complete protectionism that created a domestically oriented industry with high production costs. By 1954, Argentina's GDP per capita had fallen to less than half of that of the United States from being 80% equivalent before the 1930s. This case demonstrates how protectionism can lead to economic stagnation and a decline in living standards.