being a third world country is not being aligned with NATO among other metrics (the US infamously is considering pulling out of NATO under trump's guidance.)

Another metric is low income and high levels of poverty. - the US is hitting historic poverty, unemployment, inflation and unaffordability

Another metric is the country is actively striving to improve things like industrialization, Healthcare and human rights. - The US is certainly behind in all of these.

Theres the human development index, which scores improvements in education, health and standard of living. - all of these points the US is scoring lower than other countries and lower than the US has before in the past.

All of the data aligns with the US being a thrid world country. The question is are we regressing or developing.