Agree, but the countries aren't really in Epcot's backyard like this park would have been?
Too close to DC I think maybe even would have been a deterrent. People can spend an entire week in DC and still catch mostly highlights. (I'm here 15+ years and visit historic places all the time, and still have a bucket list

)
I think Disney could have done a history park well most likely, but too close to DC I think maybe wasn't the place for it. My initial thought was they could have explored putting it down somewhere off the I-81 corridor going south or even in central Virginia (close enough for a side excursion and isolated enough to be a primary destination). Or even another state.