He said at the UN Oceans Conference there was deathly silence after a US presentation while other nations including China, Russia, the EU and India spoke out strongly in support of the conference's aims.
"To me, that was a clear demonstration of where the global unity lay. At the moment, it's easy to see that sadly, America is isolated and the other countries are prepared to step into the vacuum of leadership that is left by America."
English later said it was clear the climate change issue was "top of mind" in the Pacific as was a belief the US was isolating itself from the region.
"That's the feeling here. The US has gone off in a different direction."
He said it had not changed other countries' commitments to the Paris Agreement or the level of anxiety in the Pacific about it.
Puna has also called for the oceans to be treated as a living entity, citing the example of New Zealand's treatment of the Whanganui River under a Treaty settlement.
He raised that with English as well, saying in some parts of the world, the ocean was effectively used as a dump and that affected the rest of the ocean.
"By floating the idea of maybe giving this ocean the identity of a living personality, so that they can have rights, maybe it is one way of drawing the attention of the whole world to the need - the very urgent need now - of us having to protect the oceans and not use it as a dumping ground."
Asked if New Zealand would support such a proposal English said it was unlikely it would go down that path, but the objective of it to manage environmental damage was sound.
"When you've got climate change concerns it's really quite a big deal and I think they're looking around for any tool they can to get better management of their oceans."
He said the Cook Islands had taken some fairly significant steps with marine protected areas and fisheries.
"We are fully supportive of the direction the Cook Islands is going, we'd need further discussion about the concept that's been floated."
Reprieve for Muri Lagoon
While in the Cook Islands English announced New Zealand would put $8.8 million toward designing a new waste water treatment for areas such as Muri - a tourist hot spot on the island where there have been concerns about pollution in the lagoon for years.
The concentration of accommodation providers and tourism operators has been blamed for the pollution because of the strain it has put on sewage systems.
English said it was an important project because well managed waste water systems were critical for public health and to protect environments such as the lagoons.
He said it would also help Rarotonga's growing tourism industry.
"The economy here is dependent on a healthy environment."
Puna said it was a pressing need for Rarotonga.
English said more than 140,000 tourists were expected in the Cook Islands this year and the infrastructure had to be robust to limit the impact on local services and the environment.
English also announced $15m towards the Manatua Cable between Samoa and French Polynesia to link Rarotonga and Aitutaki to faster, lower cost internet.
