The question offers a false dilemma of having to choose between two absolutes or admit ignorance.
Morality has to do with motive and intent, not just results, and does not exist in a vacuum. If you had to chose between saving the life of one of two people, or neither of the two, what is the moral decision: Choose one, or let both die? Is it immoral to kill someone with an automobile because they stepped in front of your car without warning, and you could not avoid it? How about if you could not avoid it because you were speeding? Or because you were texting? Or drunk? What if you got some sick pleasure killing them, even though you did not plan it and could not avoid it? Does that make the action any more or less moral? Or does it have to do with the person?
Taking a wide view, lets define immoral as intentionally harming innocent people without just cause (such as self defense) whether the harm is physical, emotional, or socioeconomic.
That said, it is no secret that some of the actions of the US government have not always met this basic moral standard. Slavery and the treatment of Native Americans are examples from the past. However, I think the majority of US citizens regret that, and encourage their government to avoid such action.
Many were outraged when it became evident that the War in Iraq was based on faulty or manipulated intelligence. In hindsight, they now see that Saddam Hussein was not an immediate threat to the US. This foreign policy blunder destabilized a region where the greatest threat, Saddam Hussein, had been contained. As a result, more Iraqis died and a different threat arose that threatens more people in more nations. It cost thousands of lives and billions of dollars.
However, this is still quite different from a nation or government that would openly employ genocide or needless slaughter to further their national interests, or would advocate its citizens committing suicide in an attempt to inflict civilian casualties.
The people of the United States and the actions of the United States government are two different things, though ultimately the people bear responsibility for the actions of the government. In a nation based on law, a "moral" populous will attempt to correct unethical or immoral actions by the government.
In my opinion, the majority of people in the United States today do not want their government to harm other people without just cause. However, in matters of national defense, the nation and its citizens will tolerate the fact that innocent people could be harmed, but hope their government would do everything possible to prevent it.