Yep, they cleared route 16, but not 23...
That would be great if they were in far, far, and I mean FAR fricking western Virginia and were pretty much headed over the Blue Ridge into Kentucky.
Not so great for getting anywhere near "Alexandria."
And there is NOWHERE in Virginia that they could have gotten that view out of the window of the RV. The elevation was far too high. There are a few places on the Virginia side that are a little higher, than the Washington side, but nothing like that.
I THINK in the comic they go to Alexandria city, which has been cordoned off. If they were that close to be able to see DC as they were, they were a lot more than half way there. They were almost there.