Americans are packed into cities too, though maybe not to the same degree. A lot of America is still just wilderness.

Well...what I really want is to get my 20s back. A do-over. Extra years would be nice, but I don't love the idea of finding a way to only slow the aging process just to watch my body deteriorate more gradually than I expected (it's already a fair ways into the process). So if it's just that, I'm only mildly interested.

It's a different study, but you might have heard about one where they basically made mice young again. You're right, a big question mark, whatever they come up with, is how we die instead. We'll have to see what role cancer and accidents play. Although, we're working on curing cancer, and automobiles, for example, are way safer than when I was born. There are car models whose rate of death is statistically zero. It's so much safer to get in an accident than it used to be.

And, as I said, we'll have to see who actually opts for treatments. Fingers crossed that right-wing Christians would rather die, but they come up with those beliefs post hoc. They certainly get chemotherapy for their cancer to delay going to heaven.

I don't see how it possibly works without severe population controls. Frankly, there's about as many humans on the planet as there ought to be, probably more.

That said, Americans will probably get first look considering the bulk of the work is being done and funded here. And the US has a VERY low population density compared to other countries -- a measly 35 people per square kilometer. Russia, Canada, and Australia with 8, 4, and 3 people per square kilometer, respectively, but they all have much more uninhabitable wasteland.

The US could support a much larger population even without taking advancements in food science into account, but with no one dying of old age, it wouldn't take too long before we reached the danger zone. We'd still need restrictions on population. Personally, I'm hoping that Christians, being a literal death cult, will decide that life-extending treatments are the devil's work and anyone who gets them is going to Hell.