Would they help or hurt our economy?
According to wikipedia, the average tariff was 1.3% in 2010. Historically, tariffs were almost always above 10%, reaching as high as 44.6%, until the post-WWII era.
My thoughts on this: We should raise tariffs, significantly, and we should do it yesterday.
Why? This would shift the balance so that manufacturers would be more likely to open factories in the US, rather than in China. I believe it could reduce or even reverse the direction of the flow of jobs out of the US. I know other countries would retaliate, but the US is a net importer. We stand to gain more by doing this than a net exporter would.
This is something we need to do soon, before the US loses its buying power. If we lose our buying power, there would be much less incentive for manufacturers to relocate to the US because they would be shipping more of their goods to other places in the world.