After yesterdays effort (which took a long time), I've decided to take another tack on answering the question.
Yesterday I got bogged down with finding evidence of numbers (or acceptable estimates of them) through research, at the expense of bigger issues, I think.
I don't think it can be disputed that "millions" have been killed by the US (say nothing of at the hands of other countries ... but this particular question is about the US).
The more important question to me is what sort of attitudes, laws, actions, etc, has led to all those deaths in my lifetime?
And also, when we say "the US" , what do we mean? I'm including government actions & policies, the policies & actions of US businesses & to a certain extent, the attitudes of (some, not necessarily all) US citizens .....
Anyway, I've just compiled a list of as many causes of deaths I can think of which I believe can be attributed, directly or indirectly, to the US. Of course, it can be argued that I'm making some judgments here based on my own values & you might disagree with with some entries on the basis of your values. Your list might be quite different to mine, but we're not here to argue the pros & cons of each others' values. It is more important to consider the reasons, priorities, the implications & the sheer scale of all those deaths, I think.
(I don't think I've expressed that very well. I hope you get my drift.)
Anyway, here's my list of deaths caused during my lifetime.:
• Deaths caused directly by US invasions & US involvements in wars ... including Vietnam, Iraq, Afghanistan, etc...... I would include WW2, if I was born a bit earlier...
• Deaths caused as a result of US arms sales to other countries
• Deaths caused by “leaders” of poor, under-developed countries purchasing US arms for regional wars at the expense of the needs of their people (like food, healthcare, provision for clean water, etc)
• Deaths caused by US influence in the UN, in support of US policy at the expense of humanitarian objectives .... eg a ban on landmines
• Deaths to troops from allied countries supporting US foreign policies (like in Afghanistan & Iraq)
• Deaths caused by embargos imposed by the US/UN on particular countries limiting supplies of food, medicines, etc (eg Iraq during the Gulf War)
• Deaths caused by US produced/ used chemicals like Agent Orange ... (both to US & allied troops & the citizens in which these chemicals were used.)
• Deaths caused by “trials” of US drugs & treatments on citizens of poor countries & vulnerable US citizens. eg http://theglobalrealm.com/2011/09/01/syphilis-experiments-shock-but-so-do-third-world-drug-trials/
• Deaths caused by the sale of unsafe products by US businesses to third world countries .... like pesticides & infant formulas by US pharmaceutical companies.
• Deaths & suicides of soldiers involved in US initiated wars as a result of inadequate post-combat treatment of conditions like PTSD ... this would not be limited to US troops & their allies, but “enemy” troops, too.
• Deaths caused by US financial & diplomatic support of repressive regimes, like Chile, Guatemala, Indonesia, etc
• Deaths caused by CIA “covert operations” in countries such as Guatemala, Nicaragua, the Bay of Pigs, etc
• Deaths caused by the sale of unsafe US products to third world countries ... like medications that have been banned in the US .
• The application of death penalty on US prisoners.
• Premature death to some poor US citizens due to the high cost of health care. (speculating here on the basis of anecdotal evidence, as I don’t live in the US)
• Deaths as a result of the ease of access guns in the US ... US gun laws
• Deaths caused by unsafe practices by US corporations in other countries ... eg the Bhopal disaster in India. http://en.wikipedia.org/wiki/Bhopal_disaster
• Deaths caused by US assassinations. eg Osama Bin Laden, drone attacks on suspected “enemies” in Yemen & Pakistan, etc
• Deaths caused by “Big Pharma” profit motives, which has made the control of Aids extremely difficult in the poorest countries in the world (which most need it) , like Zimbabwe & South Africa & countries in central America.