ISTANBUL — Iran on Friday vowed a “crushing response” to the Trump administration’s move to designate its elite Revolutionary Guard Corps as a supporter of terrorism, saying it maintains the right to withdraw from the 2015 nuclear deal. In a statement to reporters, Iran’s foreign ministry spokesman called the United States “isolated internationally” over President Trump’s decision to undermine the agreement and push for tougher restrictions on Iran’s nuclear program. In his policy speech Friday, Trump blasted Iran for its “hostile actions,” and declared the nuclear deal outside the national security interests of the United States.