Mr Brown has described himself as being "very pro-American"
It was a more positive final note after a difficult trip, overshadowed by the Pope's visit to the US and domestic economic troubles.
But in Boston, the British Prime Minister Gordon Brown was in a spiritual home of sorts, familiar territory from the many holidays he has spent on nearby Cape Cod.
This is where he chose to deliver a key foreign policy speech, a decision that went down well with Massachusetts liberals, as he called for American leadership on a range of issues, including climate change.
In a broad and almost idealistic speech, he emphasised the need for global solutions to global problems and said international institutions, set up after World War II, needed to be overhauled to deal with the challenges of the 21st Century.
He urged the UN to do more to prevent and respond to the breakdown of states, calling for "an international stand-by capacity of trained civilian experts, ready to go anywhere at any time to help rebuild states".
And he stressed that a new approach was needed to deal with problems such as terrorism or the economy, which were having an impact around the world.
For example, he said, the International Monetary Fund (IMF), rather than focusing only on national economies, needs to devise a more comprehensive approach and monitor the global economy.
Now is an opportunity for... a new dawn in collaborative action between America and Europe
The recent housing market crisis and ensuing credit crunch "demonstrates that national systems of supervision and economic management are simply inadequate to cope with the huge cross-continental flow in this interdependent world", said Mr Brown.
Mr Brown was introduced in glowing terms by Senator Ted Kennedy, who described him as "one of the finest public servants I know and I'm honoured to call him my friend".
The senator said that Mr Brown had fought "with great passion, boldness, dedication" to help eradicate disease around the globe, support food programmes, combat the threat of terrorism in Africa and put the spotlight on the genocide in Darfur.
In many ways, the British leader was trying to set out the broad lines of a post-Bush foreign policy - without saying it in so many words.
After all, President George W Bush still sits in the White House and has just hosted Mr Brown for dinner.
But Mr Brown did also meet the next president during his US visit - he had meetings with all three presidential hopefuls, Senators Barack Obama, Hillary Clinton and John McCain in Washington on Thursday.
Gordon Brown called for global economic policies that benefit both rich and poor
"Now is an opportunity for a historic effort in co-operation, a new dawn in collaborative action between America and Europe," he said in his hour-long speech at the JFK presidential library, adding that "America's leadership is, and will be, indispensable".
The message was clear - the days of unilateralism should be behind us and the post-Iraq war tensions across the Atlantic are water under the bridge.
Throughout his trip, Mr Brown seemed keen to play up the close ties between the US and the UK, telling CBS television that he is "very pro-American and I've always been".
There is a perhaps a fear that the "special relationship", which cooled after Mr Brown's predecessor Tony Blair left office, might suffer further as closer ties are forged between the US and the pro-American leaders that have recently come to power in Europe - French President Nicolas Sarkozy, Germany's Angela Merkel and now Silvio Berlusconi in Italy.
How the speech went down in the US depends on who you ask - some of the American journalists covering the event said there was nothing new or groundbreaking in the speech and criticised the fact that it did not really offer any concrete proposals.
For Senator Kennedy and many others, "it was very well received".
He said people were moved by an "extraordinary speech of vision, principle and courage", adding that that it reminded people of the common interests between the US and the UK.
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