Well, for one the EO makes it so it's illegal to have held (now to sell) such securities 1 year after they were determined to be CCP related, it also provides that the secretary of defense can list companies determined to have been CCP linked but not yet disclosed. I'm not an expert in finance but what I take from this is that there may be companies that have been determined to be connected going back a year or two+, which we will soon find out are illegal to own.

To your point, yes this will likely cause a lemming off the cliff scenario where people are looking to dump anything suspect to non existant buyers (because who is going to buy such a thing even if they're not US investors.) But the act of selling such will also be illegal in the US. I have no idea how wide spread this will be, but I wouldn't be surprised if this goes as high up as major US corps like Apple, FB, Twitter, Microsoft, etc, depending on their business connections over seas. Time will tell and I'm the last person who's advice you should hang your hat on since I barely dabble in finance as a hobby.

But I hope I helped in some way.