>>28512081America has lots of space, so they just slap in a larger engine and call it a day instead of squeezing every possible optimization possible.
Also, big blocks haven't been a thing for a while for a lot of American performance cars. There's the Viper, which is 8.4L, but that hasn't been built since 2017. That block is known to make hilarious amounts of power if tuned, not to mention it can be bored to 9.0L.