The two photos above show fuselage sections being fabricated at Shenyang China.
The Trump Administration has imposed or threatened tariffs on imports from the EU, Canada, and China, all countries which are a part of the critical supply chain for the A220. But the real problem does not lie exclusively at the top of the supply chain but rather applies equally at the roots, at the bottom. That includes raw materials such as metals. At the present time, there is no discussion coming from the Trump Administration of the imposition of import tariffs on either entire aircraft or on major assemblies, such as the A220 center fuselage assembly coming to the Mobile facility from Shenyang China. Might that happen? The supply of metal and a myriad of raw materials from abroad could be seriously disrupted by a trade war. While imports between countries outside of the US may not be affected, a trade war (especially with China) would certainly affect the development of the Mobile plant, which is critical to the success of the A220.
It is interesting to consider Shenyang. Besides making fuselage sections for the A220, this company is the only manufacturer for the vertical tail leading edge for the Boeing 787. It also makes numerous structural components for the A320 series. Shenyang is also the manufacturer of numerous military aircraft for the PRC Army, including fighters and bombers. It is easy to understand that if China-US free trade is endangered (both imports to China and exports from China) that the logistics chain for aircraft production (both Boeing and Airbus) would be impacted. Contracting with Shenyang to produce these important structural components is actually an inducement (or a concession) that encourages China to buy Boeing and Airbus aircraft. It is also an avenue through which China has acquired new technical expertise.
Would a trade war between the US and China spill over into a production disruption for the A220? It is possible. Even though the original CSeries deal was between Canada and China, and now the surviving A220 is between Airbus and China, the China-US trade dispute is certainly in play, especially with a Mobile AL production facility.