Because people are addicted to spreading their political opinions like evangelists of old.
Luckily that only generally seems to be Americans. So if you could all kindly tag yourselves in your profiles as such it would make it a lot easier to filter. /s
Sure, there’s always some low-level background muttering about politics in other countries, but the USA has really taken the cult of personality/political party to it’s absolute max.
Looking from the outside in, I pin the beginnings of this on the pledge of allegiance. Indoctrinated a whole bunch of young boomers into the idea that the USA was at the pinnacle of society, and once you blindly believe that, your eyes are closed to the actual issues. Rinse and repeat for a few generations and here we are, watching a country tear itself apart via a political system stained with polarisation, bias and narcissism.