WASHINGTON—The United States is confident Iran attacked an Israeli-managed tanker last week, killing two, the top U.S. diplomat said on Monday, predicting a “collective response” but saying he did not think the incident necessarily signaled anything about Iran’s incoming President Ebrahim Raisi. “We have seen a series of actions taken by Iran over many months, including against shipping. So I am not sure that this particular action is anything new or augurs anything one way or another for the new government,” Secretary of State Antony Blinken told reporters. Raisi takes office on Thursday. “But what it does say is that Iran continues to act with tremendous irresponsibility when it comes to, in this instance, threats to navigation, to commerce, to innocent sailors who are simply engaged in commercial transit in international waters,” he added of the attack, which killed a Briton and a Romanian. “We are in very close contact …