In which of the following situations might a trade embargo be used by the united states

There are many reasons, one can be for example punishment. If the United States disagree with a country over something they can introduce a trade embargo to prevent trade in that area until the other country changes their ways. This was common historically in central and South America, most notably countries like Cuba.

Sir thomas more, venerated in the catholic church as saint thomas more, was an english lawyer, social philosopher, author, statesman, and noted renaissance humanist. he was also a councillor to henry viii, and lord high chancellor of england from october 1529 to 16 may 1532. i found this information on wikipedia