You're not getting it.
The issue is, if UA merges with US, then will there be 744s from CLT to the west coast? The answer is a clear yes. Besides the fact that UA has said they would do this, it simply makes sense.
SFO and LAX are hubs for UA. If the merger occurs, CLT will also be a hub for UA. UA is a great example of an airline that flies its widebody fleet between its hubs. Name a hub pair, and you will find that there are currently 744s (and 767s and 777s and others) running between them. Although PIT may be, CLT would be no exception. This is not just serving the specific market of CLT-LAX or CLT-SFO, it is US Southeast - California, US Southeast - Pacific Rim, etc. Sure, people in Atlanta and Miami have nonstops to SF and LA on smaller jets. What's the difference? ATL-SFO/LAX and MIA-SFO/LAX are not hub to hub flights. CLT-SFO would be.
Also, don't forget that there are more people in the southeast that do not live in Atlanta and Miami that are going to have to connect somewhere anyways. If they connect in ATL, UA loses to Delta. If they connect in MIA, AA loses to American. You bet UA needs those widebody flights and onestops to the Pacific Rim from CLT to keep from losing out to AA and DL in the southeast.
Hub to hub flights are why the comparison to IAD is more relavant than to CVG, and certainly BOS and JFK. No one has more than an international gateway at BOS and JFK. Speaking of CVG, where do you see that CVG is larger than CLT? I'm not so sure of your numbers. Mine come from the FAA.
One last note for Imkeww: no, the west coast is not very densely populated, no matter how Hollywood wants you to believe. Have you ever driven from LA to Las Vegas? Or San Francisco to Sacremento? Fact is, California is the largest state in the Union, but not because it is dense, but because it is spacious. It takes up 3/4s of the west coast, but only has 25 Million residents. Comparatively, the states I mentioned, FL, GA, SC, NC, and VA take up about half of the east coast, and contain 35 Million. On top of that, the northeast is more densely populated than the South. This is why US Airways has been able to support the three closely positioned hubs for so long.