Early Kraftwerk doesn't have much to do with techno (other than the historical lineage). The 3 albums up to and including Ralf & Florian are only incidentally part of the musical pathway that starts with Autobahn, and are influential only in as much as the band (Ralf & Florian in particular) became familiar with electronics over those 4 years.

Autobahn is absolutely not atonal, and Trans Europe Express which was arguably the critical album in defining their connection to Detroit Techno was an extremely melodic album for the most part.

It is not true that anything about techno caught on "simultaneously in Detroit and Germany". Most people would date the origins of Detroit techno in the early 1980s. The "scene" that gave rise to it arguably originated in the late 1970s, but in 1977 that scene, like house in Chicago, was defined by the music various DJ's played, not by records being made. It was only in the 1980s that Detroit techno (and Juan Atkins in particular) actually started making records. By that time, Kraftwerk had been a band for a decade, and had already released "The Man Machine" and "Computerworld", two absolutely seminal albums.

I think you are correct to say "the use as a heavy beat dance music owes a great deal to black American dance genres." It seems fairly certain that Kraftwerk did not regard their music as dance music, or rather, they did not create it as dance music. On the other hand, Moroder had already produced "I Feel Love" in 1977 also, so the idea of electronic dance music was not in itself a Detroit innovation. HiNRG was a scene very contemporaneous with the setting up of the Detroit techno scene, and also represented the use of electronics to make dance music, and like Detroit techno, was very strong connected to existing black American dance genres.

The particular sound that Atkins et al. pioneered was very much their own, and its this sound that is what makes Detroit techno unique. And we can recognize that innovation without ignoring its origins, just as one might celebrate what the Rolling Stones did without obscuring its very clear origins in delta blues.

The wikipedia section on the history of Detroit techno makes it clear just how much the originators felt they were influenced by Kraftwerk (i.e. a LOT):

https://en.wikipedia.org/wiki/Techno#Detroit_techno

Contemporary German techno is hugely influenced by Detroit techno, much more so than a direct line to Kraftwerk. But that's a much, much later development, and doesn't have much to do with the origins of techno itself.

We should also note that Kraftwerk were also hugely inspirational to the origins of hip-hop too. What is arguably the first hip-hop record, "Planet Rock" by Afrika Bambaata, is just a mix of Kraftwerk's "Trans Europe Express" and "Numbers", topped with NY rap.

Personally, I view almost all music as evolutionary. There are very few examples of musicans or composers who truly have no precursors. I don't know how useful it is to try to talk about the origins of any particular style of music (or even just one piece of music) when it is almost always a tangled web spanning decades if not centuries in time, and often whole continents in space. And for me, most of the best music humanity has made also generally comes from a hybridization between cultures.

However, if there really are any examples of revolutionary bands or composers, then I'd nominate Kraftwerk for the category. Although albums like Autobahn, Trans Europe Express and Computerworld fit firmly into western 12 tone conventions, and use relatively conventional rhythmic structure, the music was almost without any precedent at all. Early Detroit techno sounds a lot like Kraftwerk. Kraftwerk didn't sound like anybody else at all, not even the other electronic music being made in Germany at that time.