Smoot Hawley was being debated by the Senate through March, 1930. In May, 1930 Canada imposed retaliatory tariffs and by September many other countries did as well. 1028 economists signed a petition pleading with Hoover to veto the bill.
There were many mistakes that led to prolonging the GD. Time will tell what will be the impact of piling Cap'n Trade and Obamacare on top of Porkulus and the rest.