The US is already in a trade war with China that's only escalating. The most immediate impact would be that the US could block Chinese companies trading with Cuba from access to their market.
Sure, but according to this, US-China trade in 2023 represented around 575 billions $ worth of goods (of which US goods produced in China wouldn't be immediately impacted I suppose). I guess it would depend on who gets hurt more, China or the US at the end of the day but it could have huge consequences for both countries
I think the big difference is that China produces things that the whole world needs, and it's much easier for Chinese companies to find alternative buyers than for US to find things they get from China, many of which aren't even produced anywhere else.