I know what you mean about modelling an actual location. Many of us strive to recreate past times and I think a real location would help in capturing that elusive atmousphere.
It looks great and it is true that anyting "made up" as an British engine seems to look false but with a country the size of the USA it seems convincing.
I agree with devondynosoar118 regarding polyfiller, I don't think card will look authentic. Its a shame its not worked out after all the time you spent on it.