The Smoot-Hawley Tariff wasnt enacted until after the Great Depression had already begun. The Great Depression was a global problem, not just an American one caused by American legislation. I would definately blame bad investments over things like government involvement. In the 1920s a lot people thought that everyone would soon own personal airplanes (just an example), and when people invested so poorly in dead-end companies that could never stay deliver the economy collapsed. This was similar, although to a much greater degree, to the 1990's internet economy when people were investing in companies that had no hope of staying afloat.
More importantly to our conversation, government involvement in international trade (atleast not this example) is not as efficient as the market according to economic principles. An example of government involvement in foriegn trade working is the South Korea automobile industry (huge positive externality), where Korean companies were initially too weak to compete on the global market but thanks to government involvement (mainly subsidies) South Korea was able to nurture its automobile industry until it could support itself. Essentially, no government involvement no automobile industry for South Korea.
As stated earlier, the government is more efficient than the market at providing public goods, externalities, and information.
