"Tectonic plates"? More of an earthquake
As I have said before "It is all about trust"
The USA imposes a 30% "witholding tax" on individuals taking dividend profits on USA stocks. This is reduced to 15% if a simple W-8BEN form is filed certifying foreign status. If the investor is domiciled in a country with a tax treaty with the USA (like the UK and many other countries) - the tax on certain investments (like a UK #SIPP #pension) is reduced to zero.
There is the fear that the W-8BEN acts as a very easy way to engage a punishing tax at "the drop of #trump hat".
Exchange Traded Fund managers would be very embarrassed if this screw was turned - so there is an overall trend to limit this exposure to a future trade war.