Without a strong nation like the USA to keep the Earth Federation in check, it abandoned all pretense of Democracy, and began the slow descent into totalitarianism.
First, it began a global network of censorship to prevent dissent. Then in 2000, fearing a popular revolt, it began to cite overpopulation as an excuse to murder 2 billion people via concentration camps, viruses and eugenics. Then it enslaved the rest of humanity. By the present day, The population is enslaved to the world government, with peace activists used as mouthpieces for propaganda supporting them for "bringing world peace". There is no resistance because of enhanced listening and viewing technologies making any gathering impossible, especially after curfew time (which is 8pm) when anybody outside of their "slavedorm" at that time is executed alongside their families.
This is the "boot stamping on a human face - forever" that George Orwell wrote about.