https://www.wired.com/story/china-conquers-mexican-automotive-market-and-the-us-is-worried/
State department hand wringing that China is going to use the US trade agreements as they were designed is 
I fully expect them to redo these with "except china" clauses.
to the best of my knowledge the tariff was raised to make the investment in crashing a bunch of cars to satisfy NTSB standards less attractive. cost to consumers is doubled shrinking the potential market (even if they would still be competitive with basic econoboxes sitting at $38,999, the market shrinks considerably compared to a car that would fly like hotcakes at $14k but has to be sold at nearly $30k due to tariffs.)