The EU is looking to build alternative currency mechanisms for Iran.
If China is cut off from any global trade structures, I can’t imagine any non US countries would go along with it.
The other reason for this is that all the US allies that could possibly have worked with the US on this are all under threats of tariffs from the US themselves.
It's true that Trump is strategically blundering by being overly aggressive with the Europeans, however their economic system is under greater threat from China than the US is. The EU and Eurozone countries openly support what the US is doing in confronting China, even if they have their own disputes with the US on trade.
Most of Europe plainly has even more at stake in dealing with China than the US does. The greater European region is far weaker than the US as a whole (half the GDP per capita, far less wealth, less economic growth, greater economic stagnation the past 10-20 years), both economically and militarily. China has in recent years demonstrated its ability to directly purchase votes and influence among weaker European nations. China is an advancing superpower that is pursuing both tech and industrial dominance. Europe has no tech dominance for China to plunder or compete with, however it does have a large amount of high-skill, advanced manufacturing in Western Europe. China wants to own that. What's left of Western Europe's economy if they do?
Most of Germany's economy is built on advanced manufacturing and an extreme level of exports (~32% of its economy is exports), resulting in the world's largest national trade surplus. China's goal is to move up the development ladder and to own advanced manufacturing. If China has its way, Germany will be gutted. Most of Europe's interests on China are aligned with the US. The two can likely manage to keep US-Europe trade issues separate from the need to also deal with China.
SWIFT becomes irrelevant if this happens, not China.