Let me just say clearly and without bias, as both an American-based flyer and elite on both Delta (ST) and Continental (*A)...

Both alliances have amazing cover of the United States. Before the merger of UA and CO, Delta for a singular airline trumped all with the merger of DL and NW and today maintains unique coverage of small markets in the Midwest that NW covered as well as the Southeast that DL covered. UA/CO is strong with small markets in the West. US is a throwaway to be honest. I mean, it is the ugly sister no one wants without any real specialty and in looking at their domestic map, it has limited coverage versus both UA/CO, DL and AA.

For most flyers and Americans, you're flying from major market to major market--the most populous 100 metropolitan areas of the US are all within a 90 minute drive of an airport that is covered by both if not all three alliances.

So unless you're flying to International Falls, Minnesota (which is losing all coverage (Delta) soon because of a loss of FAA subsidies) you're fine. Stop the trolling.

And really, all Americans are desperately wanting to fly JetBlue in any case.