American Sue Pemberton rushed to Havana to experience authentic Cuba before the communist island gets swamped by capitalism. The only problem: millions of other foreigners had exactly the same idea.

Already booming tourism is set to explode in the wake of President Barack Obama's visit to Havana on Sunday, when he'll bury an almost six decades-long conflict that left Cuba the last major undeveloped market in the Caribbean.

So Pemberton, 63, joined a tour to "see it before it changes."

"I assume in a few years there'll be a Starbucks and the McDonald's and Subway and all the chains," she said, while waiting for her group outside the cathedral, set in a stunning square in old Havana.

Visitors flock to see Havana's crumbling, picturesque streets, ride in pre-1960s American convertibles, and listen to street musicians playing romantic songs about Fidel Castro's 1959 revolution.

But the more they come to see a country seemingly stuck in time, the more the country changes.

"For me the attraction was getting here before everyone," said Evan Ingardia, 30, a student at the University of Washington business school, standing with two friends near a dream-like line of pink and purple open-top Cadillacs and Oldsmobiles in the city center.

Yet he was aware they were probably already too late.

"It's starting to wander between what's authentic and what's bordering on fake."

Cuba nautical tourism
A couple of cyclists pass the U.S yacht Still Waters, moored at the Hemingway Marina in Havana, Cuba, Thursday, Aug. 6, 2015. (AP / Desmond Boylan)

Floodgates crack open

Tourism dominated by Canadians and Europeans is nothing new. But the game changer was last year's restoration of US-Cuban diplomatic relations, raising the eventual prospect of unrestricted travel from a country of 323 million barely an hour's flight away.

Last Tuesday, the Obama administration tore another hole in the already tattered US economic embargo by telling Americans they can now travel to Cuba as individuals, not just as part of approved organizations.

They are still officially not tourists and have to come under one of 12 categories, such as educational activity, but the rules are now almost unenforceable. 

Of the 3.5 million tourists to Cuba in 2015, only 161,000 were Americans. However, this was 77 percent up on the previous year and Americans are now expected to be a major component in a growth spurt taking overall numbers to 6.8 million in 2018.

"We are obliged to focus entirely on this market, because there are so many of them that we don't have time for other tourists," said Nelson Calderon, a tour guide specializing in US visitors. "It's not that we don't want others, but we don't have time."

Nostalgia? No thanks

The commercialization of old Havana and other Cuban attractions may disappoint tourists searching for retro-revolutionary chic.

But Cubans themselves are utterly un-nostalgic, thinking only of a chance to escape their stifling existence in a broken-down communist economy.

"It was an era that led to a dead end, so it's good that it's changing," said Fulgencio Verderas Dias, an 80-year-old guitarist busking in a touristy street.

Yaset Martin, 30, an artist selling paintings nearby, said that "developing, not standing still," is what matters.

Perfectly illustrating Cuba's drift from its revolutionary past, Martin's offerings included the inevitable portraits of revolutionary icon Che Guevara -- but only because they are tourists bait, rather than for ideological reasons.

"I don't know the past," the artist said. "I live in the present."

Cuba tourism 2016
Tourists sunbathe as a vendor sells kites decorated with Cuba's flag on a beach near Havana, Cuba Dec. 19, 2014. (AP / Desmond Boylan)

'Theme park' Cuba?

Cuba does not have the infrastructure to handle mass tourism.

Some also fear unpreparedness for the darker kind of problems -- ranging from overbearing corporations to social ills like income inequality, crime and drugs -- that Cubans have previously kept largely at bay.

"By the time you get big business concerns and the hotels, I think you're going to see a very different Cuba emerging," said Nancy Roberts, a professor specializing in strategic planning at the Naval Postgraduate School in California, who was working with university colleagues in Havana.

"There's something special and unique about this place and is anyone thinking about that?"

Most Cubans are overwhelmingly bullish, noting their country's unusually high educational levels and strong sense of national identity.

But filmmaker and blogger Eduardo del Llano is one of the rare voices calling on his countrymen to beware the lure of the tourist dollar.

"Long term, we have to ask ourselves to what point we're going to be turned into a communist theme park where people come to see curiosities from the distant past," he said -- "and where we, to attract tourists, will have to dress up."