Ok, maybe something a little different, if this is allowed?
First off, might there be locations within the lower 48 states where *NO* AM stations are detectable (not even with SSB/BFO/CW) midday on groundwave with less than a 3-meter-per-side tunable loop or equivalent antenna?
If so, what might be the strongest skywave station received there?
Any chance that such location may possibly have the strongest skywaves NOT be Class A stations, or stations with 10kW or more transmitter power at night? Or maybe the strongest skywaves are the graveyards?
As another idea, what would be the closest you could get to one of the non-directional 50kW Class A Clear stations around sunrise/sunset, and have it completely covered (uncopyable and un-DX-able) by a co-channel station on day facilities? (Also midwinter midday skip counts, too.) Only include stations licensed within the USA - no Canadians, Cubans, Mexicans, etc. Bonus points if you're close enough to the Class A for it to trip the seek on an average radio at midday in summer, better yet if most female friends (great-grandmas to wives to great-granddaughters, cousins, aunts, nieces, etc) consider it to be perfectly listenable. (I'm referring to midday summer reception of the Class A.)

In such a case, what might be the location, the offending Class D (or Class B) station, and the affected Class A?