It will shock no one to hear that Americans are remarkably unhealthy eaters. A new American Diet Report Card (pdf) confirms it: we eat far too much cheese, sugar, starch and red meat. We don't eat enough fruits and vegetables. We consume almost 500 more calories per day than we did in the 1970s.

Our eating habits are poor, but it's not because we're a nation of lazy fools jonesing for our daily Big Mac fix, health be damned. It is because we are far too deferential to the interests of big companies, too invested in a corporate-serving narrative of personal responsibility with no parallel requirement of social responsibility, and too culturally wedded to a food model of quantity over quality.

There are some bright spots in the Report Card: we're eating less beef and sugar. Chicken and yogurt are more popular. And while wildly popular items like pizza, burritos, nachos, quesadillas and pasta may not be universally healthy and are almost all bastardized versions of their original incarnations, they do reflect the wonderful American ability to try out new foods and create a diet that is thoroughly multicultural. Fruit and vegetable consumption is depressingly low, but we've made small affordable healthy adjustments, like eating more chicken instead of beef and drinking less soda. It's certainly no coincidence that these changes are coming after public health leaders, who have been shouting about our disordered eating practices for decades, have finally succeeded in getting attention paid from the highest office in the land, in the form of Michelle Obama's focus on healthy eating and exercise.

The message is getting through, but slowly: the way we're eating is killing us. Something has to change.

Unfortunately, all of the change has fallen on the backs of consumers. In a nation where close to a tenth of the population has diabetes and heart disease is the number-one killer, our food system is a national disgrace and a public health disaster. Yes, many of us could make small choices to eat better, and many of us have indeed adjusted our dietary habits in reaction to increased information about healthy eating and increased access to healthy food. But choosing to eat well isn't an easily available option for many Americans, in large part because of structures implemented by big food companies and their agents in Congress. When a corporate food culture is setting us up to eat large portions or heavily-processed, densely-caloric, low-nutritional food, "personal responsibility" isn't going to cut it.

Large numbers of Americans, particularly those who live in low-income areas, find themselves in food deserts where there is no decent grocery store or market to purchase fresh fruits and vegetables. Instead, many low-income people really on small corner stores, which are often underwritten by big manufacturers. These mom-and-pop joints aren't exactly rolling in the big bucks, and they often rely on the perks offered by large-scale food manufacturers to put that company's products – usually chips, soda and candy – at the front of the store. Perishable goods like fruits and vegetables are more expensive and come with a greater risk of lost profits. Not only might it be more difficult to find a company to ship 12 apples at a time to a small convenience store, but if the apples don't sell in a few days, they go bad. Twinkies, on the other hand, last for a disturbingly long time.

Some of the worst foods are also the cheapest, thanks to farm subsidies that artificially depress the price of corn, which is processed into a wide array of products. Even Americans who can physically access grocery stores that carry fresh and healthy food often can't afford it. And with Congressional Republicans trying to cut $4bn from the Supplemental Assistance Nutrition Program (SNAP, also known as "food stamps") which benefits the poorest Americans, the ability to pay a little more to buy vegetables and brown rice instead of frozen pizza – not to mention the time to prepare a wholesome meal – is simply out of reach for too many of us.

It's particularly out of reach for low-income mothers, who bear both the brunt of family food preparation and also blame for things like childhood obesity and diabetes. Children with single parents receive more than a quarter of SNAP benefits, and single parents receive 13%. These families aren't exactly rolling in the free food money, either: the average SNAP payment amounts to just under $1.50 per meal.

That's not much to feed your family on, and with some of the least healthy foods the most affordable it's no wonder rates of illness caused by poor eating track with poverty.

Even outside of low-income households, eating nutritiously can be a challenge. The explosion of chain restaurants has put many smaller places out of business, hurting local cultures and erasing eating traditions. The US is a big place, and McDonald's is hardly the heart and soul of our food culture; but the more that TGI Friday's replaces local haunts or makes their businesses unsustainable, the more homogenous our plates look. Chain restaurants have the added benefit of ordering enormous quantities of meal ingredients wholesale, which means they're able to produce bigger portions for less money. Several centuries of large-scale immigration to the United States shaped our cultural identity as a land of plenty, and that ethos remains woven into our politics, our values and our eating habits. We gravitate toward these large-plate, low-cost restaurants because they hit a sweet spot in our cultural values: bigger, more, for less.

That especially makes sense in a culture where food is strongly tied to feelings of love, providing and satisfaction, and where women are largely saddled with the burden of at-home food preparation. This week, we collectively grimaced at Stephanie Smith, the 300 sandwiches woman, simultaneously pitying her for her awful boyfriend who wakes up in the morning and asks her why she hasn't made him a sandwich yet, and resenting her for adopting such a retro response. If the most efficient way to get your boyfriend to propose is to make him 300 sandwiches, you would absolutely be better suited to find a new boyfriend – you know, someone who actually wants to marry you because he loves you, not because you create a blog documenting your subservience with the most tired of sexist tropes.

Gender inequality continues to influence how we eat, and fairness-oriented political solutions would make a difference: equal pay would mean more disposable income for women to buy healthier food for their families; equal sharing of household labor would enable two-parent households to more efficiently prepare and clean up after healthier home-cooked meals; more generous food aid programs would give low-income families, which are disproportionately led by single women, a teeny bit more to invest in fresher foods.

Americans are trying to eat better – the improvements in our report card, however modest, demonstrate that. But just like kids can't succeed in school without the team effort of parents, teachers, public investment in education and a variety of resources to serve a diversity of needs, Americans won't see large-scale changes in our health until we start making wide-ranging public health efforts that go beyond demanding individual good choices. Systematic, political and economic changes are what will get us straight A's.