Blend Specifics

Bullets:
Oriental and English blends can be very similar, depending on how the blender chooses to identify a particular blend. The tobacco that tends to make an English an English is latakia -- and latakia is made from oriental leaf. So an "Oriental' blend could contain lots of latakia. . . or it could contain none at all, choosing to put other kinds of oriental leaf forward.
I'd encourage you to explore McClelland's Grand Orientals line. Only one (I believe) includes latakia: Yenidje Highlander. In addition to educating you on a few of the major oriental vairetals, it'll help you see what an oriental blend can be without latakia.
Latakia aside, though, I'd say that a blend described as "Oriental" is a non-aromatic blend that puts oriental leaf in the foreground. For example, Presbyterian Mixture, Rattray's Red Rapparee, McConnell's Oriental Mixture are all very oriental-forward blends that include little-to-no latakia.
To me, a typical "American-style" blend will be burley-based and may include additional flavorings, even if it also includes leaf such as latakia. "Scottish" -- and, again, this is just how I categorize it -- is a non-aromatic blend that includes Virginia and unflavored black cavendish; it may also include orientals and latakia. In other words, it may look exactly like an English, but with the addition of a Virginia-based cavendish. (I personally don't believe burley belongs anywhere near a Scottish blend, but that's my own bias.) Be aware, though, that the overall pipe community isn't necessarily universally behind these descriptions that I've offered.
I think Cornell & Diehl produces a ton of American-style blends. Rattray's produces some great Scottish-style mixtures, particularly Jocks Mixture and Highland Targe.
Bob

The following is from GL Pease Q&As:
What is generally meant by "English," "Scottish," and "Balkan" style?
A: “The definitions of these terms seem somewhat fluid, apart from the fact that all tobaccos bearing these appellations contain Latakia. To my mind, an English blend has a significant portion of Virginia backing up the Latakia, and orientals serve as a spice. A Scottish blend is similar to an English, with less Latakia, a more dominant Virginia character and, perhaps, little or no oriental leaf. A Balkan, on the other hand, is predominately based on oriental tobaccos and Latakia, and just enough Virginia is used to provide structure and balance.
I don't claim this is right but it's the way I view things.”
Source: http://www.glpease.com/FAQ.html
My definition of an American blend is largely BURLEY, i.e., burley based. It may be burleys by themselves or also contain Virginias in lesser amounts and perhaps topping, but if it contains Latakia, I term it an American English blend as opposed to English blends which are Latakia with VAs.
There seems to be no black and white with many of the blend categories.

Donald Duck Dunn. Love it..