The closest equivalent to SS in America would probably be something like Transformers, a long running franchise primarily used to sell toys, but with SS being much more kids oriented and generally less an expectation to be complex in terms of storytelling and development.
Huh?
Transformers has always been kid-oriented, and what I've seen of it has been no more complex than what I've seen of
Super Sentai. (My experience with TF is mainly the original '80s series, which I thought was pretty dumb for the most part;
Beast Wars/Beast Machines, which was fairly sophisticated; and
Transformers Animated, which was kind of smart but definitely very, very kid-oriented. My experience with SS is mainly
Jetman and
GoBusters, which were great,
Dairanger, which was mediocre, and part of
Zyuranger, which was so silly and kid-oriented that I lost interest.)
From what I've seen, I don't think Japanese franchises are necessarily committed to maintaining a constant age-appeal level. If anything, some of them seem to make a point of having different incarnations targeting different age groups. For instance, the first four versions of the
Digimon franchise all varied wildly from each other in tone, complexity, and maturity.
I also don't think
Transformers is anywhere near as big in America as SS seems to be in Japan. TF is more of a niche thing. I mean, we don't have big press events announcing the cast of the next
Transformers series.