President Trump’s decision has taken us back to the future as it was in 2009, a time before serious negotiations began.
This was a time when Iran’s ambitions threatened a military clash with Israel that risked dragging in other Middle East countries and the United States.
That possibility may not be imminent now, but the logic of the situation says that is the trajectory for the long term.
Mr Trump’s decision also risks accelerating the slow decoupling of America from Europe.
The president means business — or rather, he means to halt the business of trading with Iran.
Re-imposed US sanctions are designed to force other countries to reduce imports of Iranian oil and curb investments.
Failure to so do means that by November they could themselves face sanctions and find it increasingly difficult to do business in the US.
This includes American allies: South Korea and Japan are major importers of Iranian crude, the EU gets 5 per cent of its oil from Iran, and large companies such as Peugeot and Renault have made cautious investments in the country since the 2015 nuclear agreement.
In the short term, we can expect the EU nations to stand by the agreement in a bid to save it. Brussels could even pass legislation helping companies which fall foul of the US measures.
But as the months pass it is likely many governments will quietly reduce their economic involvement with the Islamic Republic.
If so, the deal is worthless to Tehran, which only signed up because its economy was hurting so badly from sanctions.
It may declare the agreement null and void and could even re-start its nuclear enrichment programme.
That would lead the increasingly hawkish Trump administration — which now includes Mike Pompeo at the State Department and John Bolton as National Security Advisor — to revisit the "fire and fury" routine Trump trialled in the North Korea stand-off.
All this lays bare the failure of the Europeans to influence Mr Trump and show how hollow the “bromance” between him and president Macron really is.
It is less of a problem for the Russians. They are happy to see fissures between the EU and the US widen, and overjoyed to see the oil price rise as Iranian crude supplies in the world market fall.
The Americans are not without support. Saudi Arabia, the UAE, Bahrain, and Israel were all highly critical of the 2015 agreement and now back Mr Trump’s decision.
The Obama administration and the Europeans argued that the deal would result in Iran reining its ambitions in to become the leading regional power, instead becoming more integrated with its Arab neighbours.
Tehran’s involvement in the wars in Syria and Yemen, and its repeated testing of long range ballistic missiles, gave lie to that.
The Israeli government was the one most vehemently against the agreement.
They pointed out that although the UN inspectors reported that Iran’s stockpile of low-enriched uranium had been drastically reduced, they had not visited all of Iran’s nuclear sites and that visits could be delayed by 24 days under the terms of the deal.
Benjamin Netanyahu repeatedly claimed that Tehran had not stopped developing other elements of a weapons programme, especially long-range missiles.
But despite heralding Mr Trump’s decision it is Israel which is the most nervous about it, fearing Iranian retaliation from its forces and proxy army Hezbollah, both of which are now just across the border in Syria.
For the rest of the year the US and Iranian governments will watch to see if other countries abide by the new sanctions, and if so, how much this hurts the fragile Iranian economy.
If it does, the recent street protests seen in Iran are likely to grow. Either way, the relatively moderate President Hassan Rouhani will see his strength within the Tehran power structure wane and the hardliners grow in confidence.
Despite this, Iran will use diplomacy to try and save the 2015 agreement and forge an unlikely common front with the Europeans.
If and when this fails, and if enrichment recommences, then the 2009 scenario will come into sharper focus again.
Tim Marshall is a foreign affairs writer. His latest book is ‘Divided: Why We Are Living in An Age of Walls’.