The human population will peak around the 2040s (and the projections for this point in time keep being revised to be sooner rather than later) and then begin its decline, with no known mechanisms short of downright government-dictated fascism that will be able to bring the fertility rates back up again
First, all the better reason to get working on healthy life extension, which will at least delay this issue, giving us time for more healthy life extension which will delay it further. The whole escape velocity reasoning works economically as well as medically.
Second, I can envision mechanisms besides fascism that can help with the birth rate, so I challenge your "no known mechanisms".
For example, I suspect, but cannot prove, that people want to have more kids, but there is a time and money issue here. Governments can choose to support parents (should this be necessary for the economic survival of the country) through things like more tax breaks for parents, more legal protection for maternity leave, longer maternity leave, subsidized daycare, etc. (I do realize that longer maternity leave has not been a very successful solution, since its been attempted, but its only one part of the problem of the cost of having kids...). Extended healthy lifespan also will help the issue, not just through delayed senescence, but through making the career cost of having young children (for at least half the population) not as extreme. A 10 year delay to have a couple kids and stay home while they are not school age isn't as bad if you have 30 more productive working years than you used to. This may help women to choose to have children earlier, when they are more fertile.
Another drawback to having kids is the physical cost to the woman. Some clever person (I forget who) once suggested developing the technology to incubate in cows. I like that idea..! At any rate, greater medical advances to make childbirth less debilitating and reduce the risk of long term effects would be worthwhile to increasing voluntary childbirth.
Yet another medical advance that would help: any improvements in safe fertility (by safe I mean, with ways to prevent the greater incidence of certain genetic conditions) for older women and men, who have more time and money to have kids.
There are things to try to fix the problem before we achieve long term life extension (at which point it becomes moot). No point predicting doom yet.
Very low fertility among the highest-educated populations also exacerbates the dysgenic effect of some backward people still having a dozen kid
True, but if you view evolution as at the gene level rather than at the individual level, its no longer so frightening. Those people still carry many of your genes. Plus, the reasons for people being backwards are often cultural, not genetic. This can be overcome.
a society that has higher fertility rates will have stronger family and other voluntary institutions, and thus less need for the welfare state
Haven't seen this born out in practice. Right now higher fertility rates generally relate to poorer countries, so I suspect the lack of a social safety net is more cash related. Higher fertility rates in the States seems to relate to immigration, and is likely not linked to your smaller (compared to Europe) social safety net. Just a guess here.
It might not seem like a terrible crisis, because technology will continue to advance somewhat and per-worker productivity will continue to increase, but it would be a huge net loss of potential nonetheless.
Do you have a solution that does not involve oppressing half your population? I honestly don't think we deserve to survive as a society if this is what we have to do.
And yes, strictly depending on the timing involved, we could get ourselves into a real problem here if the easy ways to encourage childbirth do not outpace the decline, and extreme life extension does not come fast enough. So I see the fear of fascism. But religious oppression is just another form of fascism so uh... six of one, you know. Might as well have the government do it if someone has to, it has less chance of sticking around past its "best before" date. Besides, religion generally fails at overcoming the effects of prosperity in producing more children, so its not even that simple. Birth rates in some heavily Catholic countries are low. Not as low as Japan, but low.
If necessary we could all *pay* women to have children I guess. Really extreme there, so we'd have to be truly desperate, but beats forcing them by an order of magnitude.
Isn't it obvious, for example, that a country with more young people will also have more abortions?
Not if the comparisons are per capita, which they usually are. For example, you can see a *per capita* chart of teenage birth rates here:
Source is: United Nations Demographic Yearbooks
Same idea for crime. The relevant comparisons are per capita.
However, I buy the Freakonomics hypothesis that unwanted children lead to greater crime rates (by said unwanted children), so crime in comparison to other Western nations may be partially due to cultural acceptance of abortion, which is less in the States.
And finally you have the issue of freedom - Europe used more government force to brainwash its population out of the old religion and into the new one than America has, but is that really a good thing?
I think all the religious nuts sailed over here, so I'm not sure brainwashing was even necessary =) Aside from the formerly Soviet states, I'm not sure much brainwashing was going on over there. Plus, the religions over there are very old (with a few exceptions like Wicca). New religions is more of a new world phenomenon: Mormonism, Seventh Day Adventists, Scientology, Jehovah's Witnesses... they are all American, right?