At the outset, it is important to understand the fallacy of composition regarding the depreciation of global currencies to gain an illusory export advantage. If a country weakens its currency, it will gain an export advantage, all else equal. However, nothing operates in a vacuum. When other countries depreciate their currencies to gain an export advantage, the advantage becomes obsolete and you are back at square one. The next iteration of global currency depreciation becomes a transient advantage until becoming obsolete and ending back at square one again – the dynamic occurs in each iteration.
That being said, labelling China a currency manipulator today is inherently incorrect as that is 30 years too late. The pscyhological 7CNY per USD creates its own perception of importance due to repetition/conditioning causing China to make sure it’s currency appreciates when approaching that threshold. China would likely let its currency float when the balance of payments are stable.
The point is, the combination of 1) The 7CNY per USD threshold, 2) Tariffs, 3) Investors jawboning who have an investment in CNY depreciation, and 4) Increased fear of China collapsing due to the 7CNY per USD threshold and tariffs cause depreciation in the Yuan in and of itself via capital flight. However, to label China a currency manipulator while the aforementioned actions of the United States causes depreciation is a tautology and double-standard.
Lastly, increasing tariffs on countries whom the United States imports from increases costs to consumers, businesses, or both. This also causes those countries facing tariffs not to borrow in USD because the increase in inflation in the United States will cause interest rates to increase leading to a stronger dollar, decline in exports, and more expensive USD debt for foreign countries. Conversely, the tariffs on China impacts exports in the short-term while accelerating the Lewis Turning Point, but the depreciation in the Yuan will ultimately lead to an increase in exports.