Why so few American bands in 70's prog?

 ?? Of course it limits the duration of individual tracks, since it imposes time limitations. How can you fit a seemingly endless track on a LP every side of which can only contain a limited number of minutes? The only way is to SPLIT the track into two or more parts. That’s what prog rock and jazz artists did in order to fit &release their overly long compositions. Issue solved and thus an LP's time limitations did not restrict their creativity. To think that they and "fascist" labels restricted or concealed it is a fallacy that torments you and makes you still bitch about f**king absolutely nothing like a paranoid preacher.

 " Keep on supporting and believing in the quality of the materials you are getting and listening to."

Moshkito's codename for "modern art sucks"

 " One day, you might wake up and find that the difference between a fascist state and a "democracy" ... is not really that different, when it becomes a corporate run development, and that is what it all has become."

 Tell me you are an anarchist and it would be the funniest line I've read on this forum.

 "It's only problem is that MAGICALLY all pieces of music became 20x20 ... and that has always bothered me horribly ... "

Since you like Miles Davis, let me remind you Dark Magus, just one more LP far from the "hated" 20x20. Hopefully that thought of yours will now no longer bother you horribly.

 "... and now you are adding another "limitation" to the progress in that music"

No need to repeat my first paragraph.

Blaqua wrote: ...  Don’t forget the very tight time limitations of vinyls. One-hour songs don’t fit on one side of an LP and in fact even two sides weren't enough! Also, why listen through such a long endless improvised song, when you can just listen to its gist in a few minutes? Quality over quantity. ...

The LP does not, and never did, limit anything. You are now stating that the length of all Beethoven's Symphonies fit perfectly on a Vinyl LP, and that is not the case, and never was. They were all of varying lengths and parts of it taken out by the conductor to make the length necessary.

It's insane, and I think crazy, to think that all Symphonies, including Mahler and Tchaikovsky and everyone else, had them at 20 by 20 and perfectly matched to suit a LP that was created over 100 years later, and specially when in the early days, the LP could hardly handle 10 minutes. Thank goodness the symphonies did not get cut!

Many of these, and I have not studied this as well for 40 years, appear to have had movements created in the continuity to help the whole thing fit into a LP.

Miles and GD and many others could easily do this and release it, if a record company was willing, but they weren't and wouldn't, and continually thought that the band had to have a radio piece. Miles did not have a radio piece, and at the time, was not considered a major artist, until later when he finally hit his zenith.

Klaus Schulze has pieces that are hours long ... and even the LP releases never really hurt them. 

Blaqua wrote: ... Relax and unwind moshkito, no State will keep you from enjoying your arts.

Classical music, even if taught at schools, wasn’t rooted in the US culture, wasn’t part of it. The same holds for medieval history and affiliated elements and it is not odd that US artwork or lyrics associated with the Middle Ages, castles, queens or knights were uncommon. No group stateside could ever write the very British or European In the Court of the Crimson King or Pantagruel's Nativity.          

 "America, however, had one other horrible thing. It had no respect for the arts"

"appreciation for MUSIC, which the USA lacks in general"

 These are one hell of generalizations. You imply that the US lacked bands and artists playing quality music during the period in question and that this was not being promoted or released??

 " guess what you don't find released at all ... Miles used to play for an hour non stop ... have you heard one of those pieces? You won't either! The Grateful Dead used to play all night and have pieces an hour long"

 Don’t forget the very tight time limitations of vinyls. One-hour songs don’t fit on one side of an LP and in fact even two sides weren't enough! Also, why listen through such a long endless improvised song, when you can just listen to its gist in a few minutes? Quality over quantity.

 "And this is what the "media state" has done"

Relax and unwind moshkito, no State will keep you from enjoying your arts.

Early prog rock drew on classical music, i.e. European invention. Experimental US rock in the 70s drew on the American genre of jazz and psychedelia, hence much more jazz-rock and psychedelic releases.