The answer is burley. There is no more iconic American pipe tobacco than burley. From there, I think you would need to cull through the available burley blends to narrow down the best representation of the epitome of American blend. Also, there's likely to be some worthy discussion as to whether aromatic classics should be considered. I vote no. For a truly classic American blend, I think you have to choose between straight burley and untopped or very mildly topped burley blends. The other yardstick is classic American blends aren't over-strong. I know this is subjective, but, it does disqualify powerhouse blends like C&D Big 'n' Burley. Off the top of my head, I'd put the following in the final group to pull from:
Sir Walter Raleigh/Granger/Prince Freakin' Albert
Sutliff Edgeworth Ready Rubbed Match/Lane Ready Rubbed
Sutliff Walnut Match/H&H Chestnut
Sutliff Revelation Match
Sutliff Holiday Match
Carter Hall/H&H Chatham Manor
Sutliff Match Barking Dog
Sutliff Match Briggs Mixture
Edward G. Robinson
Iwan Ries 3 Star Blue
Velvet
If you really want to consider aromatics, I'd go with:
Sir Walter Raleigh Aromatic
Sutliff Match Bourbon Street
Sutliff Mixture No. 79
Sutliff Fox & Hound
Half & Half
Captain Black White
Heine's Blend
Kramer's House Aromatic
Paladin
Lane HGL
Lane 1Q
Lane RLP-6
There are a ton of modern mixtures that would be good to think about, but, to me, since they're new, they are not really iconic in themselves, but, are tributes to the iconic blends, kinda like a brand new Shelby Cobra. It's not as great as an original, but, it's still pretty damn cool. Some to consider:
C&D Junkyard Dawg
C&D Epiphany
C&D Americana
C&D Briar Fox
C&D Pegasus
C&D Old Joe Krantz
C&D Haunted Bookshop
C&D Morley's Best
C&D Old Court
Daughters & Ryan London Dock
Daughters & Ryan Two Timer
Drucquer & Son Inns of Court
E. Hoffman Distinguished Gentleman
Sutliff Count Pulaski
Cheers,
Chili