"Russian Math" seems to just be "More Math".
The basic education concepts at ploy here are well known, just not widely deployed.
Why? IMO it's because of what I think is the sole problem with american education - parents themselves not caring if their kids actually know anything. It's actually common, extremely common, for american parents to think that the point of education is to get a piece of paper (degree) or to get a job. And a large number of the parents that think the point is actually knowing things also put no pressure on the school systems to actually provide that.