Justin Webb has delivered the 2010 John Harvard Memorial Lecture - entitled Ripples from Across the Pond: Can the Special Relationship Survive? - at the Unicorn Theatre.
"It's a huge honour to be involved," said the BBC Today programme presenter who spent eight years as senior correspondent in the USA. The lecture series was founded in 2007 when Southwark and Harvard University celebrated the 400th anniversary of John Harvard's birth.
"John Harvard was baptised in St Saviour's Church which is now Southwark Cathedral in November 1607," said Southwark Council leader Nick Stanton who introduced the speaker at the Unicorn Theatre in Tooley Street on Thursday night.
"America's relationship with the outside world is complex," Justin Webb told the audience of Southwark residents and London-based Americans.
"There is this statistic that people quote endlessly about Americans not having a passport. Americans didn't until recently need a passport to visit Canada, Mexico or the Caribbean.
"America is a hugely outward looking country. In the flyover states you are long way from other parts of the States but there is a genuine interest in the outside world. And there has been a genuine interest in us.
"America has a decision to make over the next few decades. It's a decision that will be made at the time of the Mayflower celebrations [in 2020] when most of Southwark Council will decamp to Massachusetts.
"Is America at its core still centred on the relationship that there was between it and Europe?"
He said that there was a sense that America took on a set of core values brought over on the Mayflower and these have taken up by other settlers as the many immigrants are called.
"There are many Americans who believe that to be the case and there are many Americans who beieve that if that is not the case America will fall apart."
Answering questions from the audience, Justin Webb discussed the influence of American television, the US administration's view of the British Government and the experiences of Americans in London.
"He was educated at St Saviour's Grammar School and Emmanuel College, Cambridge.
Harvard emigrated to the new colony of Massachusetts in 1637 but died a year later aged only 31. Leaving no heirs, he bequeathed half of his estate and his library of 400 volumes to what was then called New College but is now known as Harvard University."