Back in the day, nations that didn't qualify as either developed (First World) or developing (Second World) were by default Third World, impoverished, corrupt and what we now refer to as failed states--governments that were incapable of improving the lives of their people and the machinery of governance, generally as a result of corruption and self-serving elites, i.e. kleptocracies.
Is the U.S. slipping into Third World status? While many scoff at the very question, others citing the rise of homelessness, entrenched pockets of abject poverty and the decaying state of infrastructure might nod "yes."
These are not uniquely Third World problems, they're symptoms of a status quo that's fast losing First World capabilities. What characterizes Third World/Failing States isn't just poverty, crumbling infrastructure and endemic corruption; at a systems level these are the key dynamics in Third World/Failing States: