https://www.historichotels.org/hotel...search=top-nav
As far as the US, people might find this link (this map) helpful and interesting for getting ideas.
In Tampa, the Hotel Floridan (or Floridan Palace), I have stayed a couple times at and it is pretty nice and comparatively reasonable rate overall. Of course, the place could do with certain updates. But, in general I really enjoyed it.
https://www.google.com/search?q=flor...w=1366&bih=625
Cleveland has a few impressive old hotels also. Most notably, the Hyatt Regency at the Arcade, where my wife and I got engaged. The rooms themselves I think are kind of modern with nothing particularly unique, but the building itself is an absolute treasure (like, on a national or even global scale), and has a great location right across from the most bustling section of Downtown Cleveland:
https://www.google.com/search?safe=s...24.q_xSefxKcp4
Mexico City is absolutely chock full with stunning hotel spaces. We stayed at the Hampton Inn right there which had a beautiful stained glass ceiling and certain portions of the building which dated to 1700s. Right nearby though (we didn't stay, but did take advantage of the rooftop bar there), is the Grand Hotel, right on the Zocalo. It has so much chops that it was featured in a James Bond movie. An absolute masterpiece, here are some pictures:
https://www.google.com/search?safe=s...30.Aus_PKB7qJA
As far as certain bucket list hotels. So, the AIA came up with an "America's Favorite Architecture" list a few years back. While I don't completely agree with it's validity, it definitely honors some of America's most iconic and inspiring buildings. These are the 10 hotels ranked highest, along with their overall rank among buildings in the country (various building types were rated).
1. St. Regis (New York City) (16th)
2. Hotel Del Coronado (San Diego) (18th)
3. Bellagio Hotel and Casino (Las Vegas) (22nd)*
4. Ahwahnee Hotel (Yosemite Valley) (26th)
5. Old Faithful Inn (Yellowstone) (36th)
6. Delano Hotel (Miami Beach) (39th)
7. Waldorf Astoria (New York City) (46th)
8. Mauna Kea Beach Hotel (Kohala Coast) (55th)*
9. Disney World Swan and Dolphin (Lake Buena Vista) (70th)*
10. Willard Hotel (Washington DC) (76th)
11. Broadmoor Hotel (Colorado Springs) (78th)
12. The Plaza Hotel (New York City) (81st)
13. Sofitel Water Tower (Chicago) (82nd)*
14. Fairmont Hotel (San Francisco) (89th)
The reason of course I did more than 10 other than that I found the list fascinating, was that some modern structures were ranked highly too (at least in the case of Swan/Dolphin which I stayed at-I felt it deserving). The reality is that there are so many hotels out there that perhaps many could argue for others being ranked higher. But generally speaking, these are some of America's most iconic hotels.