I think this article would have been stronger if you had researched the definition of "third world country" before writing it.
The term originates in the post-war world to refer to countries allied with neither the US nor the USSR (socialist or socialist allied countries were "second world").
More recently it's used to refer to countries with high mortality, especially infant mortality, rates & a vast gap between wealthy & poor citizens.
Not adopting the metric system (there are many other countries that ostensibly use it, but also use their traditional measures, such as in the UK where weight is still expressed as "stone") doesn't make a country third world. There are benefits to the imperial or SAE system of measures, especially when measuring people, e.g. someone tells you he's 182 centimeters tall, what the hell does that mean?
Gun control, capital punishment, public health ... these might be areas in which the US is less civilized than say some European or Asian countries, but they don't characterize a nation's status as first or third world. In fact, many on the far right would argue that in true third world countries, where people are poor & oppressed, they also lack access to weapons.
Regarding the Supreme Court, I took one example, France. Its highest court, the Constitutional Council, consists of two former presidents of the republic & up to nine other jurists appointed by the President of the Republic, President of the Senate & President of the National Assembly.
So, also political. The SCOTUS's life-time appointment is intended to liberate justices from political considerations. Sometimes it does, e.g. the Warren Court.
Point being, I'm not sure what method you would propose to appoint justices that would be more "first world".
Don't get the wrong here, the US's infant mortality rate is shamefully high for a nation as wealthy as this. And the widening gap between ultra-rich & poor/working class is disturbing. The US is not a third world nation by any standard definition of the term, but there are trends gradually leading us there.