If the US government confiscates physical gold, do you think it would still be possible for retail traders to trade spot gold using cash-settled transactions?
Extremely unlikely in today's political environment. If they confiscate gold, then most likely it means that US Citizens will not be allowed to own gold bullion and most likely will not be able to trade it within US borders(even if it's cash settled). However, you can always head over to another country if needed and trade it on a foreign exchange.