The State Department spokesman issued a very short condemnation  of the Tehran attacks:
The United States condemns the terrorist attacks in Tehran today. We express our condolences to the victims and their families, and send our thoughts and prayers to the people of Iran. The depravity of terrorism has no place in a peaceful, civilized world.
The statement is fine as far as it goes, but the message in it is absolutely the bare minimum one would expect in response to attacks that claimed at least a dozen lives. It should not be difficult or controversial for top government officials to denounce these attacks in the strongest terms just as they would if they had been carried out against any other country. Unfortunately, because the country in question is Iran our government has had almost nothing to say about the attacks. This is all the more regrettable because the group that claimed responsibility for the attack also happens to be an enemy of the U.S. and many other countries in the region. Expressing sympathy with Iranian victims of ISIS should be no more difficult than expressing our sympathy with the group’s Iraqi, Syrian, and Western victims. It should be easy to show solidarity with civilian victims of terrorism regardless of where they live. Our leaders should make clear that we reject and abhor terrorist tactics no matter who uses them or which country comes under attack.
The Bloomberg editors made  this point well:
Trump wasted no time condemning the spate of recent terrorist attacks in the U.K., and the same reaction is called for now. The murder of innocents is wrong, always and everywhere.
Update: The White House finally released a statement, and it’s an embarrassment:
The Trump administration issues a statement essentially blaming Iran for the terrorist attack against Iranians: pic.twitter.com/rYVxyfBSle 
— Daniel Dale (@ddale8) June 7, 2017 
This is not only a crass and insulting message to send to Iranians, but it is also diplomatically tone deaf. Instead of making a show of support and solidarity, the White House essentially blames the victim of an attack for inviting it. I know this administration is full of obsessed Iran hawks, but this is pathetic even for them.