It has the potential for the most dramatic long term consequences as it could dramatically speed up China's rise. China's economy is where future growth is, to get access to that growth capital will reallocate itself around these trade barriers to China's advantage if they persist.

Also, part of the reason the US dollar is the chief world trading currency and the US Treasury is considered the world's safest investment is open trade policy. This preferential place in the world financial system gives the US economy major advantages, including low interest rates.

Attacking the entire world at the same time is a really bad plan. The chance of wringing concessions from China would be much greater if the US would make common cause with the EU, Japan, etc. But the opposite is happening, the rest of the world is moving on w/o the US as we saw with TPP and the recent EU / Japan deal. Expect to see things like China start canceling deals w/ Boeing and inking new deals with Airbus.

Finally, there's a military dimension to this. China is raising tariffs on US oil at the same time it is saying it won't respect Trump's sanctions on Iran. Its unlikely anything would happen in the immediate term but if this situation persists its not far fetched to imagine things getting tense.