I believe the Mojave Rattler is the most venomous in the USA.
South America has plenty of nasty cousins to our rattlers.
Mojave Rattler
The mojave green rattlesnake.
Mister green can be very angry and come after you.
Ive seen three in my hike into the mohave desert
Absolutely correct. The Mojave Green is the most poisonous. They are one of the only two I think in the world that has a unique “dual” venom.
“The Mojave Green Rattlesnake’s venom can be either hemotoxic (toxins that attack the blood) or neurotoxic (toxins that target the nervous system) making treatment challenging.”
https://www.ndow.org/species/mojave-green-rattlesnake/
Our family used to own a ranch in the Mojave. I have lost 2 horses to Mojave Green bites. They were gone in less than 20 minutes. It shut down their respiratory system and they suffocated. Figure an estimated 10 minutes for a human.
Fortunately they tend to be fairly docile. You really have to step on them or make them pretty mad before they will strike. They try to get away as best they can first.