The definition of what type of business is caught by US sanctions is very wide and is likely to catch any UK business with a US subsidiary or which is doing business in the US.
At the moment the sanctions are against various Chinese companies in the Xinjiang region of China who are allegedly using forced labour, mainly from the Uyghur population in that area, to make cotton or other related products.
However, there is another Bill waiting to be passed by the Senate which imposes sanctions against goods coming from the Xinjiang region.
As a large percentage of the top grade cotton in the world comes from Xinjiang the passing of the second Bill is going to cause issues, particularly for clothing brands, with their supply chains and where to source alternative high quality cotton.
UK brands will need to audit their Chinese supply chains to first ensure they are not using any forced labour, and then consider whether to diversify and have one supplier for the US from their suppliers in Vietnam or Indonesia (by way of example), and use their audited Chinese supplier for the rest of the world.
Since it is likely that the UK will bring in some form of sanctions of its own in the future UK brands should be looking at their Chinese supply chain now and using the time between now and when sanctions come in to diversify.