I'd like to point out that the way timezones are currently drawn, there is
already an edge to the timezone. Currently because of the 1-hour granularity, people at the edge of a timezone would be approximately 30 minutes ahead or behind solar noon. Going to two timezones (east & west) would simply increase the maximum variance from the
already existing 30 minute deviation to a maximum of 60 minutes. Granted, even the 30-minute remark is laughable since current boundaries are designed around state boundaries, not actual proximity to the solar noon for each time zone.
Also the assumption that businesses would not change their hours is unlikely if the nation went to a single timezone. China and Alaska serve as examples of that. Still, doing two timezones & eliminating DST wouldn't be a dramatic change for America, and yet would still make the human interaction aspect of nationwide business easier and thus more profitable through efficiency.
Again, if arguing against the 2 timezones thing, look at how crazy-freaking wide Central already is at the southern end, or how wide eastern is at the northern end:
I can't find anything that describes exactly how far each extreme is away from solar noon, but I guarantee it's more than 30 minutes already.