Churchill and FDR agreed. The US needed to enter World War 2, but Franklin Delano Roosevelt, had to carry the people with him, and it took the bombing of Pearl Harbour for that to happen.
And so ended a two-decade period of relative US isolation.
Many fear that under Donald Trump we may see a repeat. But frankly, whoever the US president is, there is a feeling in the US that it can no longer act as the world's policeman. Those who stood against Donald Trump for the Republican nominee, the likes of Jeb Bush and Marco Rubio, who did support a more national agenda, were swept away during the early stages of the Republican campaign.
As Robert Kagan argued in the FT, the narrow interest-based approach to US foreign policy, which summarised its thinking in the 1920s and 1930s, 'plays well with a US public that has come to believe that the US has been taken to the cleaners.' It's a view that Mr Trump has played to.
It's odd because across much of the world people have been calling for less US interference, but for quite different reasons. Maybe they will get what they wished for, maybe they will regret their wish.
It is also odd because there was a perception before 9/11 that the US was becoming quite isolationist, it was the war against terror that changed that.
But if the US does take a back-seat, who may replace it?
When it comes to international trade, China is trying to fit into the boots that Uncle Sam was wearing. TPP, the Trans Pacific Partnership, the trading agreement due to cover most countries, with the obvious exception of China, that border the Pacific Ocean, appears to be dead. It's an opportunity for China, as Chinese President Xi Jinping, said recently: “China will not shut the door to the outside world but will open it even wider.”
Or maybe we will see some kind of pact. Marine Le Pen appears to be vaguely pro-Putin, but frankly, France seems to be swinging away from the US anti-Putin approach. Francois Fillon, the favourite to become France's next president, has been highly critical of the approach currently adopted by President Hollande. And recently, Jean-Luc Melenchon, another man in the running for French President, and on the left side of the political spectrum, recently said: "Francois Hollande's attitude is unbearable. We are completely aligned to the United States. We are running ahead and that attitude is not in the interests of France."
But across the EU there is political chaos. If Le Pen becomes the next French president, exit from the EU seems inevitable. There is also a risk of EU exit resulting from the impending election in Holland, while in Italy, if a referendum on constitutional reform called by its Prime Minister, Matteo Renzi, throws up a no vote, many predict an election in Italy will follow, which risks Italy's exit.
Maybe these are the worst possible times for the US to take a step backward, as we risk seeing a re-run of pre-world war 2 nationalism.
But maybe we are seeing one significant reversal, whereas in 1939 Germany was the premier force for nationalism, Angela's Merkel's decision to stand for chancellor in Germany's election next year may mark a force for stability and liberal values.
It is just that when others look at the euro crisis of this decade, the rise in inequality in the developed world that has been occurring since the previous decade, they say it has been exacerbated by austerity. And Germany, and maybe Cameron/Osborne, were its architects, the world order may be changing, it is far from clear how it will end.
The hope comes in the form of new technologies making the issue of nationhood irrelevant, instead we gather in groups of shared interests which have nothing to do with borders.