Yes and I think stations in Toronto, Balt., and Binghamton have to be protected too. I was in VT last yr and was having trouble picking up WVMT Burlington (I was in Rutland and it was nr sunset). WCRN was OK; as for WRKO, it kept fading in and out and mostly I was getting Hannity...that was from Baltimore (99.7 from NH came in sometimes)
You both are evidently quite astute concerning radio. So you may already be familiar with ``Radio Info'', a website showing both the AM and FM facilities.
Just for the record (and others may find this of interest since there a lot of technical types on FR), here's the Boston market. Click on the yellow 'i' image to the left of the calls which opens a page where the day and night coverage areas can be examined. The maps are rather optimistic in terms of actual signal penetration.
The intersting thing about 850 KOA in Denver is that it reaches 4 Canadian provinces, 35 states in the US and most of Mexico north of Mexico City, but it cannot be heard in the Seattle market since an all sports station in Tacoma is on 850 kHz. Hardcore AM DX'ers have heard KOA Denver in countries such as Sweden and Australia.