It looks like discussion of these developments is getting quite scattered around FT. Please feel free to join us over in TS&S for a general thread on the executive order situation.

But to answer the question posed here about the situation with transit countries, it's my understanding that Canada is admitting green card holders (which is business as usual; Canada generally allows green card holders 180 days' free admission regardless of country of citizenship). I'm not sure exactly how CBSA is dealing with student visas and other non-LPRs unable to cross the border or pre-clear, though there is evidence out there that Trudeau's government is trying to help.

I'm aware of at least one case where a Yemeni is unable to get out of one of the Gulf hub airports and unwilling to go home for fear of persecution - a real-life "The Terminal" situation. A lot of the details on the trapped-in-transit situation are coming out on various activist Twitter feeds, which may or may not be reliable sources.