1st, China's building up their military. As Frederic Bastiat said, when goods don't cross borders, soldiers will. A trade war with China could turn into a violent war, possibly WWIII.
2nd, the quality of China made goods isn't that bad, and certainly isn't worse than American made goods would be and have been; just about everything in my PC and the case is made in China, and it works fine, had great build quality, etc. Neither country is Japan quality, but Japan has quit manufacturing nearly everything.
3rd, it hurts the poor to have tariffs on China made goods. If people had to pay an additional 20-25% on nearly every PC part they buy, every game console, etc., then protectionism wouldn't be worthit. If American manufacturers to want to sell things, then they can make better quality things, and they can sell at better prices, like the Japanese did all those years ago.
4th, our corporate tax is too high and is going to be even higher, too much to take advantage of protectionism. In relation to the high corporate tax, our labor laws our too tyrannical, and there is too much red tape when starting a business in America. Plus we've got minimum wage laws.
5th, to achieve the maximum effect of protectionism, the dollar would have to be further devalued, which would be insane.
The only good thing I can think of that a protective tariff would do is bring in more revenue and tariffs aren't as bad as quotas as you at least have a choice--if you can afford it.
You forgot to mention the horrible effects of previous tariffs. The first on that comes to mind are the ones that kicked off the "Civil" (really a tax revolt) in the Southern United States in the mid 19th century. The second was the Smoot Hawley tariff that at the point where the Depression was just getting started, manged to shutdown the entire world trading system.
So now the USA wants the Chinese to raise the value of their currency, although better for the people of China, it is not good for the Chinese Mercantilists.
My view is that the currency stuff is a red herring and that the real issue is that the Government wants the market to over value its car companies that it is trying to sell. Of course buying their stock is really a stupid test but there are lots of stupid people out ther.