Why? And why are "saving" and "investing" equated here? (Isn't it, for example, precisely a problem in Japan that too little is being invested?) And why does that lead to low interest rates? And why is "the situation in the USA different"? Well, in part I do have some thoughts as to why certain things might be so, others are really more like "huh?". Overall, this is too much of "That is of course so. That is how it is connected. Period." I can’t even necessarily contradict it; I also simply lack knowledge on this, but I also have the feeling that sometimes overly strong causal connections are assumed when there are still quite a few other factors involved. (Or at least that’s how it comes across in the explanation)
That other things (war, supply bottlenecks, etc.) currently have a much stronger influence has already been widely noted (and yes, I am aware of that, not disputed here either) – but suddenly one is no longer at "because we have A, B will happen" but at "because we have A, and I assume that X and Y will pass, and Z will remain, B will probably tend to happen in the long term"
The central bank sets the interest rate as an investment incentive. The lower it is, the higher the incentive. In Japan, relatively little is invested BECAUSE saving takes place. Investments are made at the macroeconomic level through loans and run ahead of savings in money. That’s how our system is structured. Banks don’t lend the money of their savers.
America has a super-flexible labor market (hire & fire, extremely mobile population) and is therefore already at the beginning of a wage-price spiral, since there is now almost full employment. The government’s growth impulses in response to Corona really generated momentum. The FED not only has additional mandates compared to the ECB but also faces a different task. So it must act differently in comparison -> more interest rate hikes.
This leads to an appreciation of the dollar against the euro, which makes our energy purchases even more expensive – a dilemma. If the ECB follows with interest rates to dampen this, it risks a recession. Now there are camps that oppose each other: a recession is to be preferred over inflation or exactly the opposite. However, this always assumes inflation from the self-reinforcing wage-price spiral, not from external supply shocks.
At the moment, building is quite problematic from every perspective – little material, expensive, interest rates are rising. This will balance out when demand collapses – but then the recessive character becomes apparent.