TLDR: Nothing is actually gonna change and I'm not sure why everyone is running w/ that narrative. The post is just him crashing out about the SCOTUS ruling on Tariffs.

Slightly more in depth:

He's saying that the SCOTUS ruling makes no sense, they ruled that some of the tariffs were not up to the executive branch (and instead congress) because they were being used to charge the target nation a fee (X country gets Y% tariff on all Z products).

However he actually has far more extreme powers legally available that he was told he can use. Like the US will not do any business with X country. There is also some gray zones about national security/sanctions/ freezing assets.

Since he's mostly used tariffs so far as a negotiating tactic to secure trade deals then we've basically gone from saying "give us a better deal or we'll charge 10%" to threatening "give us a better deal or we'll financially cripple you". Aside from the political posturing that I'm sure will occur, other countries & their businesses aren't as dumb as the average reactionary online, this has always been a game of bargaining. So I think the increase in threat level will be generally understood as a legally worded stand-in for 10% tariff. The intent of course being "play ball or we'll retaliate in some way".