What if another country arrested trump and put him on trial?

I will go out on a limb and say that if the country who detained him had any trade with the US then that would cease immediately.
So, no exports to the US, no imports from the US.
I will assume the US will block all trade into and out of the country from all sources.
As we have seen, if the US wants to "kidnap" a world leader it is quite capable of doing so.
Think about the film, Saving Private Ryan.
This scenario could occur. A mass incursion of US troops would see President Trump liberated.