The term "third-world" was coined early in the period of the Cold War and referred to the countries, mainly recently post-colonial, aligned with neither the industrial West (the "first world,") or the Communist East (the "second world.") Since most of these countries were pre-industrial or industrializing, they were thought of as "underdeveloped" countries or "developing" countries. In other words. poor.
Stereotypically, they were thought of as having a mass of poverty stricken people, ruled and dominated by a small, wealthy elite. High birth rates, lack of mobility, unequal access to education and wealth (such as land), lack of health care, high unemployment and hunger were all considered "typical" for the "third world."
Reality, as always, was far more complex than this simple stereotype. The influence of this stereotype, however, underlines the kind of struggles faced by these countries, especially the newly post-colonial countries which were carved out by the colonial powers for their own interests, giving little or no thought to the interests or needs of the colonized peoples. In varying degrees, the defining features of this stereotype became part of the American worldview, such that referring to a country as "third-world" indicated poverty, backwardness, disease, hunger, etc.
Right-wing talkers, especially one well -known for many years in New York, complained that the U. S. was "becoming a third-world country" because of immigration from non-European origins. Obviously, his reference was racist. He may, however, have been correct in his assertion for far different reasons.
Over the last 3 decades, changes have been accumulating in the United States that do not bode well for the future. The growth of economic inequality between a small elite and the majority has increased. Poverty has increased. Unemployment has become endemic, access to health care has declined as costs have increased. Public education, a cornerstone of American social and economic success, is in trouble. When 25% of American children live in poverty, where "food insecurity" (read as "hunger") persists and is widespread, where the rate of social mobility is among the lowest in the industrial world, America, truly, is becoming a third world country.
The Affordable Care Act ("Obamacare") is an attempt to modify one part of the trend, but whether we look at hunger, education, unemployment (and their cousin, poverty), there don't appear to be any serious attempts to reverse the decline. The Right complains about "throwing money at problems," but seems okay about "throwing money" at large, successful corporations. What passes for their "new" ideology "Objectivism," as promoted by the atheist loony-tune Ayn Rand, is little more than re-heated left-overs of Social Darwinism. The conditions they advocate would be familiar to Charles Dickens. Just listen to hypocrite par-excellence Rand Paul who hates Big Government so much that he refused to accept Medicare when he was in medical practice.
Oh, wait. he made most of his income from "Big Government" payments for his patients!
If one looks at the great successes of 20th century America, rapid social mobility, the beginnings of racial justice (just beginnings), access to public education, such programs as the Space Program, the Interstate Highway system, the GI Bill, etc., they all involved "throwing money at problems" with astounding results. Scientific research, medical developments, economic expansion all thrived under generous public financing.
If, in fact, America was becoming poor through lack of wealth or lack of resources, if the wealth of the country was actually flowing out, it might be possible to comprehend the reasons for this trend. The fact is, however, that the wealth and potential of the United States is not declining. What is changing is the lop-sided distribution of wealth and the growing income disparity between the small elite and everyone else. That is, in its own way, a recipe for disaster for most of us.