Early British Prog vs American. Discuss.

Wow, that's some statement, rhetorically, do you really mean that? rhetorically....

Yea and i think that's why american prog rock is more jazz influences whereas british prog has more classical inspiriations

The relevant point is, based on the question in OP, whence come the avant prog tendencies in American prog? Can we trace avant influences backwards from Zappa? And find other contemporary or later musicians who drew on the same influences? Are any of them more indisputably prog?

What else should I hold it to?  There are points where it becomes like let's just throw PA wide open to all artists doing something progressive without being pure jazz/classical.  Ilayaraja is progressive and I bet you've never heard of him. But he is more progressive than the entire rank and file of second tier and beyond also rans of prog.  But that's not what matters.  It's ultimately a website devoted to prog.  If I wanted to, I could make a convincing argument for why Jeff Buckley's Mojo Pin is progressive.  It doesn't strictly follow verse chorus (there is a Hindustani tinged vocalese section after one of the choruses rather than leading right back to the riff).  On this website, even getting Metallica added to a prog-related category took a lot of fighting and that is even though Justice for All is clearly more progressive than most of what Nightwish or Within Temptation have done.  

So it doesn't work that way.  We have to draw certain boundaries just so we understand coherently what is prog.  It doesn't seem like Terry Riley is generally regarded as progressive rock nor Annette Peacock so I go with the consensus.  PA has sub genres like prog metal or neo prog added on BECAUSE they were generally regarded by the prog community as prog.  OK prog metal polarized opinions but over a period of time, people have come to accept the overlap. One doesn't see a similar overlap in this case.  

And it's hardly an insult to Riley or Peacock to say they are not 'prog'.  Would you feel insulted if I said Morricone isn't prog? But of course he did avant garde work.  And maybe you could stretch that slice of avant garde to say he was prog too if you wanted to but what purpose would that serve anyway. If it were up to me, I wouldn't have Miles Davis on the website but hey ho, that's another day, another debate.