Each answer is a place, landmark or attraction in the United States or Canada. The answers traverse all Canadian provinces, Canadian territories, U.S. states and the District of Columbia. This is done by crossing land borders where possible, although in a couple of cases crossing the sea is necessary as there are no land connections.
Each clue is missing a state/province name from another clue. (Not the answer to that clue, just the name of the administrative division.)
Note that some long names have been shortened. For example, if the full place name is "Xyz Royal National Park", the answer will be just "Xyz" (often with "royal national park" or similar as the definition).
1. Islamic extremists leave chaotic {43} USA salad to historic settlement (1'4 3 7)
2. {34} capital's borders hold extravagant Hopis regarding museum (9)
3. Anne's farm actor Clark and family coloured like {15} bay (5 6)
4. Familiar Margaret's top {11} vehicle duos produce fishing village (5'1 4)
5. Rapids turning around cliff's bottom, Cool J in author {24}'s birth initials (9 5)
6. National park's academic beginners with {4} finalists (6)
7. Actor Phoenix and second striker George follow series filmed in {64} canyon (4 5 5)
8. Region's east becomes west for {52}'s starters next to monarchy (9 7)
9. Primate and heartless CEO in briefly backwater {23} peninsula (4 3)
10. AC/DC bassist is after top-three {7} wine to stroll passageway (7 5 4)
11. Former {42} governor Eleanor familiarly leads to public park (8 4)
12. Felines unwell in short {57} back mountains (9)
13. Short {10} strangely cued a retired Wachowski waterway (6 5)
14. Fur post finally keeps top cards in {5} top two by the fifth street in hold'em (5 5)
15. Biblical figure's top-three {35} water park (4'1 3)
16. "The Knife" in a capital conundrum next to {3}'s last resort area (8 6)
17. Short {49} between pillars by haphazard sauna den sand formations (7 5)
18. Resort town president with top billing outside {12} capital's borders (3-2-3)
19. TV's Gomer east of {17} neighbour resort town (8)
20. Strike east twice from excited {21} in half-hearted book by ocean namesake town's pathway (8 4 9)
21. In front of seashore, bathe vigorously with {53} outsiders returning to coastal city (7 5)
22. Ford follows half of {26} capital with event host to stronghold (4 7)
23. Obelisk is {60} memorial structure (10 8)
24. Plantation east of {8} with one string instrument (10)
25. Historic town's sharper leader goes right, actress Tina embraces {48} capital couple (7 5)
26. Bullets and finally brought rich cognac within the edges of {50} govern central cavern system (7 4)
27. Elegance with {22}'s ending mansion (9)
28. Aged {61} capital is historic district (3 5)
29. Cay of friends having {33} loner is barrier island (4 2 5)
30. Forest's peculiar echo in {63} lake follows discussion (13)
31. National park's island near {51} mysteriously loses poles, takes five before finishing classes (10)
32. Coasts by body of water west of {31} resort city (4 6)
33. Without question, Vicky with rest of {19}'s capital leads to siege site (9)
34. Fifteen minutes behind {2}'s language neighbourhood (6 7)
35. Greek exclamations about the western part of {37} capital city (6 7)
36. Mountain city's {9} capital gets incomplete ransom for body (7)
37. Skyscraper or peach-shaped {29} building losing fluid for actor Bruce (6 5)
38. Settlements from {32}'s end with strange anise around colon (5 8)
39. Dale leaves {44} suburb, with deceit makes natural landmark (6 5)
40. Old cattle town is {16}-made car (5)
41. Lake's broken head following broken heart of {38} (6 3)
42. Battle site's returning {39} city not high end, keeps head low (5)
43. In the case of {27}, a soup brewed bloating heads leading to native community (4 6)
44. Lucky charm to twist a {46} River meander (9 4)
45. Half-fleecy westward ravine following {55}'s first and second national park (5 6)
46. Hold speech alongside {20} road with no turn to mountain (5 4)
47. Geyser not adulterous after initiating {41}'s long distance (3 8)
48. {13} band with additional mountain (8)
49. {6} loses foot, access lobster cooked within cottage (7 5 5)
50. Meeting place for short {40} (5)
51. Even {45} or steep mountain (4)
52. Okinawa city and {14} twins inspire top national park (7)
53. Gold rush town or {62} capital has endless dawn for a start (6 4)
54. Mountain's odd diesis holds {1} initials (6)
55. Last twos of East Asian capital and {59} make national park (4)
56. Mountain town to bar a duo from {36} capital (5)
57. Flexible EU skis alongside the shores of {25} lake (8)
58. Battle site is small, born holding {28} capital finishers (6 7)
59. National preserve to half-heartedly create soft heroin in designer {56}'s heart by beginning moonlight (7 2 3 4)
60. Volcano street next to {58} capital making a short head (2. 6)
61. Body of water's confusingly rare talk inside {47} capital's borders (6 4)
62. Left insane next to {18} company's man-made barrier (6 3)
63. {30} capital scorcher held in dodgy wash riff waterfront area (9'1 5)
64. Mountain top monitors a nuke blown up within {54}'s borders (5 3)