Looking from the outside, I think US political discourse IS far more hostile.
Britain won't accept things like Politicians being harassed, or one politician calling for other politicians to be harassed (and that's before we even get to anything Trump related).
And the amount of references I see to "civil war" when wandering across anything relating to US politics (i.e. not zero) is disturbing.
But the absolute number is larger, even ignoring the population size, so not sure what the person I was replying to means.