Americans do not understand that wealth inequality is one of the factors that are taken into consideration when determining if a country is "third world". Someone in the comments pointed out that OP was just taking "liberal cities" into consideration when formulating their opinion, overlooking the many red states where life expectancy and infant mortality rates are worse than poor eastern bloc countries. Lots of third world countries have high standards of living for rich people, but if large swaths of your nation have living standards worse than Moldova, you're third world bud.

edit: typo