Several commentators have questioned Wellington's ability to maintain a strong relationship with China - NZ is still the only developed country with a free trade agreement with Beijing - while it resumes its close relationship with the US after the nuclear rift.
Dr Campbell said it was hard to describe how pleased he was with the progress of the relationship.
"We fully understand that New Zealand is not looking to go backward to re-create a relationship of the past," he said, "but to re-create a strong, multi-faceted, multi-dimensional relationship for the 21st century.
"This is pretty much the model of how we want to do business. I think we have about as close a relationship as two countries can have now."
And he credited the personal regard President Barack Obama had for Prime Minister John Key for the improvement.
"I see President Obama regularly in meetings and I see the leaders that he is attracted to and he has to deal with a huge number of people.
"The truth is there are three or four leaders in Asia that he [strongly] respects and kind of listens to when they talk.
"It's Prime Minister Lee in Singapore, it's Prime Minister Najib in Malaysia, SBY (Susilo Bambang Yudhoyono) in Indonesia, Lee Myung-bak in South Korea but Prime Minister Key is in that list."
Dr Campbell had dinner with Foreign Minister Murray McCully on Friday night and talks with officials on Saturday.
Among the issues covered were the improvement in the relationship, next steps in defence, the Trans Pacific Partnership, climate change, the North Korean missile test, sovereignty issues in the South China Sea, the tuna treaty, what to do next on the Ross Sea reserve, development work in the Pacific, the elections in Japan and South Korea and how to interpret the new leadership in China.
Dr Campbell has been the Assistant Secretary of State responsible for East Asia and the Pacific, and has overseen the "rebalance" of US policy towards the Asia Pacific region.
He has also overseen a rapid resumption in close relations with New Zealand, including the strategic partnership known as the Wellington Declaration signed by Secretary of State Hillary Clinton in 2010, and the ban on military exercises lifted.
Dr Campbell hinted that the next development in defence could be a leading role for New Zealand in the move towards greater regional co-ordination of humanitarian and disaster relief.
"I think we are also going to see opportunities for greater, what you might call minilateral training and operations that I think will involve other northeast Asian states."
One of the impressive things, he said, was how effectively New Zealand had worked with countries as far afield as China, Japan and others.
'The truth is that our relationship is really blossoming very substantially and I think we want to embed some of the things we are doing militarily in a multilateral context working with other countries."
Dr Campbell said the United States was mindful of local sensitivities.
"We are constantly checking and making sure that the way we are doing things is commensurate with expectations, that is strongly supported by the New Zealand public."
He added that Mrs Clinton and President Obama had "Pacific sensibilities".
