After months of piling pressure on Tehran, the United States is seeing an unexpected new variable — the novel coronavirus, which has taken a substantial toll not just on Iran but inside its government. US policymakers are asking whether deaths within the regime are widespread enough that they could alter decision-making — although a deadly rocket attack Wednesday in Iraq, which Washington blamed on Iran, showed at least that the cycle of conflict between the countries is not abating. COVID-19, which has infected tens of thousands of people around the world, has hit Iran’s government unusually hard, with a number of senior politicians and officials killed or infected by the disease including a vice president, a senior adviser to the foreign minister and a powerful cleric.