Ethan Fidler is a 10-year-old from England who has spent six weeks in Florida and by now is missing football. Many would think him a lucky boy, and indeed he is – not because of Disney World or the beaches but because the the British national health service was willing to fly him four thousand miles and pay upwards of £50,000 for specialised radiation treatment for his brain tumour.

The NHS – often derided in the US as "socialised medicine" – sprang into action for Ethan and there is every likelihood he will be cured. His doctor at the University of Florida institute of proton therapy in Jacksonville, Danny Indelicato, is delighted with him. His mother, quantity surveyor Julia Fidler, who has been in Florida with Ethan throughout, while his dad, Mark, stayed home with their daughter, is astounded.

"I was amazed. To be told that this was something that could happen for Ethan – I was staggered," Fidler said. "To just be told that all this is going to be available for your son. It gives you a massive sense that they must really feel they can cure Ethan or they wouldn't go to these extremes. Every parent must feel that. It does give you confidence."

Ethan is in the US because the NHS as yet does not have proton therapy machines, although the UK government has just agreed to fund two of them, in London and Manchester. But while the British boy is getting cutting-edge cancer treatment here, others who live in America are struggling to obtain the medical care they need. And when they are seriously ill or have a long-term condition, many will not be able to pay the bills that pile through the door. Two-thirds of personal bankruptcies in the US are related to healthcare costs.

Ethan had been suffering from bad headaches that would not go away. Childhood cancer is very unusual. Doctors told Fidler it was a hormonal migraine and suggested a food diary and migraine tablets for her son. Eventually he had an MRI scan on 13 February, was taken in to Alder Hey hospital in Liverpool and had surgery the next day, which successfully removed what turned out to be a very aggressive cancer called an anaplastic ependymoma.

Within days, doctors were talking to the Fidlers about Florida. "The tumour leaves tiny cancer cells [when it has been cut out]. They have to blast every bit of Ethan's brain that the tumour has touched," said Fidler. Proton beams have been shown to do less long-term damage to surrounding healthy tissue in children's brains than conventional radiation. By 18 March, just a month after the operation, Ethan and Julia were in Florida, starting the six-week course of daily radiation treatment. "It was just a whirlwind," she said.

The British national health service is often accused of rationing treatment: Indelicato helped set up the guidelines to decide which child from England should get proton therapy and which should not. He says the guidelines are helpful. Children who are unlikely to benefit should not be taken away from their home and loved ones in what will be their final months. Desperate UK families who are rejected sometimes launch appeals in local papers and online to raise funds to take their child themselves. Indelicato gets an email a week – and he says no.

"On my computer right now I have an email from a patient who was turned down by the NHS for very valid reasons. The email says we have the money – we want to privately fund it. I have to convey to this family that I have never met that it is not about money at all. I say that at least once a week."

The institute, so thoughtfully designed and decorated that it hardly seems like a hospital, is part of a university. The staff are highly commited to their patients – particularly the children. If an American child needs proton therapy, they will usually find a way to take him, says Indelicato. Most will be covered by the federal government insurance safety net, Medicaid. If not, there is a pool of charity money they can call on.

But not everybody in the US with cancer gets the treatment they need. The costs of healthcare in the US are extremely high and good insurance coverage is unaffordable for many Americans. Around 40 to 50 million people are uninsured, even though they work. The jobless and poorest are caught by Medicaid, the jointly federal and state-funded safety net. So while some well-insured people may be over-treated, others are struggling for care.

"We have all the technologies, but there is a group of people who don't have access," says Dr Eric Sandler, a children's cancer doctor at Nemours hospital in Jacksonville and a board member of the American Cancer Society. "So our system is really quite broken when you have millions of people in this country who don't have the wherewithal to access the system.

"We have some of the best treatments in the world and our outcomes in specific populations are as good or better than anybody's in the world, but there are populations in our country who don't benefit from this. Some people are turned away with cancer or if not turned away completely, can't get the care they need, or the care is different if you can't afford it. We have the two extremes: care that keeps going and going when you would say it is probably futile – and the other end of the spectrum."

It greatly concerns the society's cancer action network (ACS CAN), which represents patients. "We run a call center out of Texas for any kind of cancer question," says Steve Finan, its Washington, DC-based senior director of policy. "Over 50% of the queries are from people who can no longer afford their coverage."

The organisation is nearly 100 years old and for most of that time was focused on education and research and community service. The fight against tobacco was a priority. In the 1990s it set targets to bring down the numbers with cancer and the deaths. "But in the early 2000s, they realised the numbers weren't going down, but up. They set out to ask why. They concluded maybe the biggest single issue was inadequate access to care. Too many patients were not getting proper care," says Finan.

The organisation backed President Obama's healthcare reforms. It took Dan Brodrick from Tennessee before Congress to tell the story of his wife Sharon, who died from cancer. Brodrick tells how they approached 300 different insurance companies for cover but were turned down because of a pre-existing condition that had nothing to do with cancer. So he called one of the country's leading cancer hospitals, which said it would cost $145,000 for her to begin treatment. "So I said 'What bank do you want me to rob?' And the lady says, 'What do you mean what bank do I want you to rob?' She said 'You don't have insurance? Well I guess she's going to die, ain't she,' and put the phone down," says Brodrick.

Even the insured have to pay a percentage of the medical bills (the co-pay) – often around 20%, but it can be more. That puts people off going for a screening or seeing the doctor and delays diagnosis, which makes them less likely to be cured. But when it comes to treatment, many people find their insurance – if they have any – will not cover what they need. "A lot of insurance that is sold in this country is inadequate – it's junk insurance," says Finan.

In Maine, he says, the most popular premium is one that has a $20,000 deductible. That means the patient pays the first $20,000 of care. "People buy it because the premiums are low, but they don't have the savings to cover it so they don't ever get to the insurance. It is catastrophic coverage but the math doesn't add up. $20,000 is an enormous amount for most Americans. We are not a savings country. They don't think it through. The level of insurance literacy is very low in this country," says Finan.

A survey ACS CAN commissioned in 2010, after the healthcare bill passed but before it took effect, found half of families dealing with cancer had problems affording the costs of insurance premiums, co-pays or drugs. Just under a quarter had been contacted by a debt collection agency. One in six had incurred thousands of dollars of medical debt.

There is a belief in some quarters, says Finan, that anybody who needs care will get it, because if you go to the emergency room, they are obliged to treat you. "It's absolutely not true. Hospitals are only required to stabilise you. Once they have, they can dismiss you," he says. That's no good for those with chronic conditions like cancer.

The patient network, together with the American Cancer Society itself, representing doctors, and the American Diabetes Association and the American Heart Association, filed a friend of the court petition in January in support of the Affordable Care Act when the supreme court heard the case to have it thrown out brought by a number of states who allege it is unconstitutional.

But the patient voice often gets lost. "Business interests are winning out over health interests. The bottom line is that it is about money," says Finan. "People have lost sight of health."