“Frankly, it made no sense that the United States consistently, essentially made the decision to isolate ourselves from the rest of the Americas because we were clinging to a policy that wasn’t working,” said Ben Rhodes, the deputy national security adviser for strategic communications. “So we would anticipate that this does help begin to remove significant impediment to having a more constructive engagement in the hemisphere because we demonstrated an openness to engage all of the countries in the Americas, and to include Cuba.”

Washington’s critics accuse the White House of maintaining a longstanding US policy of interference in Latin America, evident, some say, in its approach toVenezuela.

“What the sanctions also made clear, for those who didn’t already know, is that President Obama’s opening to Cuba represented exactly zero change in Washington’s overall strategy toward the region: The intention of expanding commercial and diplomatic relations with Cuba was mainly to pursue a more effective strategy of undermining the Cuban government – and all of the left governments in the region,” said Mark Weisbrot, co-director of the Center for Economic and Policy Research in Washington. “Basically, Washington still hasn’t adapted to the idea of an independent Latin America despite the game-changing geopolitical changes in the region over the past 15 years.”

But Venezuela – long the sharpest thorn in the side of the US in the region – is in a far weaker position than in the previous two summits. Maduro lacks the charisma of his predecessor Hugo Chávez, the fall in oil prices has weakened its influence and economy, and the government is struggling to cope with deadly protests, shortages of basic goods and the highest inflation rate in the world.

With the crisis growing, Maduro is finding it hard to rally regional support. When he called Dilma Rousseff to discuss the summit this week, the Brazilian president cooly stated that her government was ready to help him strengthen dialogue with the domestic opposition and welcomed Venezuela’s willingness to reduce tension with the US.

The change in economic climate is also working in Obama’s favour. Three years ago the US economy was still emerging from the post-crisis doldrums while Latin America was benefitting from a Chinese-driven commodities boom.However, GDP growth in South America is expected to be nearly zero this year, while the US is enjoying rapid growth and the strongest dollar in a decade. Pragmatic regional leaders may calculate that they can no longer afford to upset Washington.

The Obama administration meanwhile has more reason than ever to engage with its neighbours: the increasingly important Hispanic vote in the US, which wants progress on key regional issues such as drug policy, immigration, Cuba and the economy.

The Panama summit will also aim to strengthen regional cooperation on climate change, disease outbreaks, water usage, drugs, education, crime and elections. Colombia is also likely to receive support for its efforts to secure peace with Farc and other rebels.

Having grown used to a lack of consensus at previous summits, these initiatives are likely to go ahead regardless of squabbles, but nobody expects major progress.

“An agreement is not that important,” says Juan Gabriel Tokatlian, international studies director at the Universidad Torcuato Di Tella in Buenos Aires. “Unless the summit system is able to concentrate on extremely few and crucial issues we will see more events without great substance … I believe the most positive things that could emerge are Washington announcing that Cuba is removed from the list of state-sponsors of terrorism and an overall support for the Colombian peace process. If so, these two issues could to some extent ‘save’ the Panama meeting.”

A change in the regional winds

The political and economic shifts among the major players at the Summit of the Americas:

Venezuela

2012: Sitting on the world’s largest reserves of oil at a peak of $125 to the barrel, President Hugo Chavéz had the economic influence as well as political charisma to lead the charge against the US.

2015: As the oil prices have more than halved, Venezuela under Chávez’s successor Nicolás Muduro is suffering recession, rising poverty, the highest inflation in the world and deadly protests. Its crisis is now a major concern for neighbouring countries.

Brazil

2012: After two years of rising commodity prices and steady growth, Workers Party president Dilma Rousseff’s approval ratings were over 60% and the country was looking forward to an offshore oil boom that looked set to reinforce its position as the dominant economy in the region.

2015: About a million protesters marched against the government and corruption at the state-oil firm Petrobras in March, the economy has slipped closer to recession and Rousseff is the least popular president so far this century with approval ratings in the low teens.

Argentina

2012: Having easily won re-election the previous year thanks to rapid economic growth and a 50% reduction in poverty, President Cristina Fernández de Kirchner was a strong regional figure and close ally of Chávez.

2015: With nine months until she must stand down, Kirchner is a lame-duck president. The economy is in the doldrums and hundreds of thousands took to the streets in January to protest the suspicious death of a prosecutor.

United States

2012: Barack Obama is isolated and ridiculed at the Summit of the Americas over the US policy of excluding Cuba. The US economy is still recovering from the 2009 financial crisis.

2015: Obama wins kudos for moving to normalise diplomatic relations with Cuba. The US dollar is at its strongest level in 10 years against many Latin American currencies, encouraging regional businesses to look north instead of toward slowing China.

By Jonathan Watts