It seems more likely that the Strait of Hormuz is just in the possession of Iran without grander implications for maritime trade.
What would other countries do? If the US's military might is powerless to control Iran, what chance would any other country have here?
Trump's weakness in giving up the illusion of US power certainly would be a disaster for the US, and world trade, but broader implications seem unlikely.
What can Iran do if other countries consider Iranian ship as free for the taking as retaliation for Iran attacking ships in the strait of hormuz?
What would Australia do if Iran attacked their embassy? They would kick them out, denying Iran an embassy in Australia. When it comes to this stuff, a tit for tat strategy is generally the common tactic. If you attack peaceful trade ships, then your own trade ships is valid target for retaliation. If you start to threaten ships with ransoms, other nations will do the same.
Invading Iran is a complete different subject compared to boarding trading ships well outside the border of Iran. Historically, a Letter of marque was a very cheap way to manage countries which did not respect your own ships. Some laws are still in the law books regarding how to deal with prize ships, which illustrate how close we are to the time where peaceful traversal of waters was not a given.
One of the biggest trade partner for Iran is China. Will China pay the toll? Will Iran attack their ships? Will China retaliate if they do? If China do not need to pay the toll, which other countries would then be willing to one-sided pay for access to the strait?
> What can Iran do if other countries consider Iranian ship as free for the taking as retaliation for Iran attacking ships in the strait of hormuz?
This is exactly what Trump tried. The US was boarding Iranian ships thousands of kilometers away. In the end the US still backed down and agreed to an Iranian toll in the MoU.
Iranian ships have been getting boarded for extremely flimsy reasons for over ten years now. That forced them to adapt to it in such a way that they are now far more resilient to it than the rest of the world is.
What would other countries do? If the US's military might is powerless to control Iran, what chance would any other country have here?
Trump's weakness in giving up the illusion of US power certainly would be a disaster for the US, and world trade, but broader implications seem unlikely.