Really? So the population has to always increase? When does it end?
> American population and culture is in no danger of dying off
Neither is japan's. You could argue that japan's population and culture will last longer than america's.
I look at say Japan and they've got all this history, art, literature, customs, even essentially their own religion. Their culture is very distinct.
I look at Russia, Austria, England, France, most of the rest of Europe and Asia and see the same thing. They have their own art, history, customs and behaviours that are quite distinct from one another.
But I don't see America's culture. I suspect the problem is that American culture has been exported throughout the western world so much that it's hard to tell it apart but I'm not sure.
* Philosophy: the concept of philosophical pragmatism and big contributions to economic and political liberalism
* Music: Aron Copland, Leonard Bernstein, Gershwin, Duke Ellington, Jazz, ...
* Architecture: Frank Loyd Wright and a lot of contributions to modernism
* Literature: Hemingway, Faulkner, ...
If you want to talk about "customs", a mindset typical of a country that sets them apart from the other cultures you described, the most typical American trait is a pioneer belief, a radical optimism with very little regard for traditions. That attitude permeates the list above.
In that sense it lacks some inherent culture because it's a collection of different people who came here from all over the world. Japan (and most other older nations) has a shared ethnic and religious identity that goes back centuries or millennia, whereas America by definition doesn't really have that. Instead it's an amalgamation of all of the different people who live here. To me, "American culture" means going to downtown Mountain View, CA for dinner and getting to choose from dozens of amazing cuisines from all over the world (with varying degrees of authenticity, but still).
Even food/cultural artifacts/etc. which are strongly associated with America tend to be things brought here from other places and cultures and adapted to local tastes.
The "blood and soil" people are especially alarming to me because what they're most passionate about is attempting to retcon America into being based on religious/ethnic/geographic identity politics rather than what actually makes America somewhat unique and successful, which is simply the fact that it's based on ideas rather than tribalism, and was designed as a haven from tribalism in other countries.
I'm sure someone will read this and get all up in arms about the gazillion times America has done horrible things that went against the very ideals that I just described. Trust me, I know. I'm not trying to idealize everything and sweep that stuff under the rug. Every country has always and will always deviate from its own principles, but it falls on patriots (as opposed to nationalists) to do whatever they can to help steer it back in the right direction. Patriotism should be about fixing things when they go wrong, not "my country right or wrong".
I doubt Japanese culture will survive this century, but it is only seventy-odd years old.