Not true at all,
Not to split hairs,
New York has only two other similar stations, WFAN, and WCBS, and there are some others like them scattered around the country but they are rare when compared to the total number of AM licenses. The Philly market has no non-directional 50-kw stations.
Yes, there even is an upstate AM on 770, but it is a three tower directional daytimer aimed almost exclusively at a Canadian audience, with its transmitter very close to Lake Ontario. It offers ethnic programming and identifies itself unofficially as "WTOR Toronto." It is no threat at all to any reasonable WABC daytime groundwave audience, and it is likely relatively few Americans could even listen to the signal if they wanted to. And the 770 in New Mexico, never threatened WABC's primary audience. That's not true on a lot of other frequencies where there are massive night-time co-channel problems, and compared to those stations WABC does have a "clear channel" frequency, whether the old full country definition still stands or not.
As far as all the new electrical interference problems go, there is no doubt that they are discouraging AM listening, but they have an equal impact on all AM stations, and a 50-kw non-directional low frequency signal has a whole lot better chance of overcoming the local interference than a lower power directional at the high end of the dial. It's just physics. And those are the reasons why I said "WABC (is) something special compared to the rest of the AM pack." It is rare beach front property, and that is the objective truth.