Can a couple of bullets really seal the fate of millions? Virtual JFK introduces audiences to virtual or counterfactual history - the 'what if?' scenario. It asks: what would have become of the Vietnam War if President John F. Kennedy had survived the assassin's bullet in 1963 and been re-elected in 1964? Would there have been a Vietnam War at all?

It is all well and good to say that Napoleon would have won the battle of Waterloo had he made more sensible breakfast choices (and thus not been plagued by stomach ulcers, constipation or other digestive ailments), or that the Roman world would have skipped a vicious civil war if Cleopatra's nose had been shorter or Mark Antony avowedly gay, or that Europe's golden age would have continued if Archduke Ferdinand's car had taken a different street in Sarajevo in 1914, or that there would have been no Tiananmen Square massacre in 1989 if a few of the Chinese Communist Party's faceless men had been less worried about their next promotion.

However, if we're going to do virtual history properly, we need to go further than this documentary and think about how one player's choice intersects with another's, and put together an argument about where all this leads in the long term. Sometimes in history, what seems the right decision at the time turns out to have all sorts of unintended, unforeseen consequences - good intentions do not always yield good results.

This example of counterfactual history asks the right question - and builds a strong and riveting case through narrative, logic and images to prove that this is the right question - but then barely begins to give the answer.

The case that JFK would have opted out of Vietnam is built using illuminating examples of Kennedy's decision-making on questions of war or restraint. These include the Cuban missile crisis, that horrendous 13 days in 1962 when the world came to the brink of nuclear conflagration and when the US military bluntly saw war as the only choice; the little-known beginnings of the conflict in Laos; and also the Berlin Wall confrontation, when the president personally had to stop provocative US tank deployments.

The documentary leaves us in little doubt that a second Kennedy Administration would not have opted for the creeping military enmeshment in a Vietnamese civil war, let alone the wholesale deployment of hundreds of thousands of young Americans and the massive unleashing of air power, napalm and the rest.

But what would have happened next? Would the 1960s have been a decade of peace, light and love if the United States had decided that Vietnam was not its problem? The alternatives to the Vietnam War might have been bad, too. And how differently would the Cold War have turned out?

For completeness, it would be fair to ask Southeast Asians today what they think of the war and what might have been. There would still have been conflict and suffering, even if on a much smaller scale. No matter how distasteful it might be, there's an argument quietly prevalent in some circles that the Vietnam War bought time for most of the recently-independent nations of Southeast Asia to develop with relative peace and protection, and that it is one of the reasons why most of Asia for the past few decades has been calmer and more prosperous than at any other time in history.