Which requirement would be the "killer"?
So there's still hope, winterkjm!
Its not that I doubt the US could re-submit under Deferral and be successful. But there are several individuals who could easily decide this world heritage tag is not worth the effort, and conceivably the nomination may expand or decrease, so some of these stakeholders may have just wasted their time (in their view), or the nomination will become even more complex. Consider the breadth of this nomination already covers 7 states which distance would span all of Europe in comparison. Referral has the appearance of near success (recognizing OUV)
, while Deferral is perceived as more of a roadblock. I am not saying this is actually true, because re-worked nominations can be very successful, but US budgets for the world heritage program are not huge, nor are the workings of UNESCO and ICOMOS common knowledge.
In my communications with a NPS staff who helped oversee US nominations, it was often stated how difficult this nomination was in organization and getting all owners together, to agree on the nominated components, and to get buy in from all stakeholders involved. I just searched old posts and we first had rumor of a FLW nomination in January 2012, with inscription for 2013. I have emails from 2013, where NPS staff expected to submit the nomination in 2014 as well. This nomination was delayed, pushed back, a couple times before it was finally ready for the 2016 WHC. That's ignoring the sites extended history, when Taliesin aimed for inscription more than two decades ago.