Funny how a story gets repeated and accepted without question
It only took me a few minutes to find that reference showing that the "smallpox blankets" apparently happened but before there was a United States or a United States Army. The guy who did it was British but our Army has been slammed for many years for something that apparently happened before it existed.
There may have been other instances besides this one and all would be deplorable. Still, it appears the US Army and the United States itself has been falsely accused, at least in this case. By no means does that mean atrocities weren't committed by the United States Army against the Indians. Lord knows they have enough Indian blood on their hands for later incidents like the Sand Creek Massacre.