You can sort of do it on the Marriott site, but only state by state (or country by country) and it is cumbersome to do.

If interested:
Go to the "About Marriott" section, "Our Brands", then just chose a brand (does not really matter which), and click on "hotel directory". In the next screen you'll have the options to add the brands you want to the search (this is the cumbersome part), and then just click on the state or country you want and chose map.

I have not figured out a better way of getting there.