Earlier quoted context omitted.
Trump changes plenty, in the past it was assumed that the USA would honor visa once they were issued, now it turns out not to be the case. Essentially this is breach of contract.
in the past it was assumed that the USA would honor visa once they were issued What do you mean by "honor"? A visa don't guarantee entry. It simply gives you a path to enter the country which includes inspection by immigration control. They make that very clear on the USCIS website and all the visa forms. A U.S. visa in his/her passport gives a foreign citizen permission to apply to enter the United States. A visa by…
That expectation has been violated by recent actions, because green card holders with no black marks were turned away or prevented from even coming on the whim of the president. That devalues something like a green card dramatically because it could be rendered meaningless one day by fiat.