That is because most other countries have multi party systems.
The polarization is still there, but spread thin amongst various factions.
In the US, people are shoehorned into R or D.
Edit : I would also like to point out that the OP is a bit confused between cause and effect. In the US, the effect is deep polarization. However, the cause is the power of mass communication, especially misinformation and blatant lies, that FB enables and does not bother to control. The cause is common to all the countries in the world, the effect varies due to various other factors, one of them being the presence of a multi-party system.
Take the example of India. FB has a large and active user base. However, India being a chaos of various identities, cultures, regions, languages, etc, divisions in society are less pronounced as there are a large number of players (politically, regionally, locally, etc)
Other than that, the effect of FB in Europe is also less visible due to the same reason. Every EU country has mostly multi party systems, leading to spreading thin of the hate and focus.
Because Canadian electoral system is also FPTP just like US and UK. Our election results already reflect this: decades upon decades of essentially only two parties ever being in government and almost no coalition governments.
Most European countries have functional multiparty governments because they have some variation of proportional representation.
The UK doesn’t have a true multi-party system. First-past-the-post elections all but ensure there are only two dominant political parties. It’s really only been a game between Labour and Conservatives for longer than most of us have been alive.
The Lib-Dems were part of Cameron’s coalition government if memory serves. Ironically the former leader of that party (Nick Clegg) now works for … Facebook.
And, you have deep divisions there. If you perceive one single enemy, all your efforts will be focused on that one. If you have three, your efforts are spread out.
This makes the divisions, rhetoric and social environment seem less severe, but the problems are just as big.
The polarization is still there, but spread thin amongst various factions.
In the US, people are shoehorned into R or D.
Edit : I would also like to point out that the OP is a bit confused between cause and effect. In the US, the effect is deep polarization. However, the cause is the power of mass communication, especially misinformation and blatant lies, that FB enables and does not bother to control. The cause is common to all the countries in the world, the effect varies due to various other factors, one of them being the presence of a multi-party system.
Take the example of India. FB has a large and active user base. However, India being a chaos of various identities, cultures, regions, languages, etc, divisions in society are less pronounced as there are a large number of players (politically, regionally, locally, etc)
Other than that, the effect of FB in Europe is also less visible due to the same reason. Every EU country has mostly multi party systems, leading to spreading thin of the hate and focus.