Theme: Mountain Range. Each theme entry contains the name of a mountain range, and in each case it begins and ends with the first and last letters that name - hence the use of "range" in the unifier clue. Let's start there.
37 A. What each set of circled letters spells ... and depicts: MOUNTAIN RANGE. Self explanatory. But could be baffling if you didn't get the circles.
17A . Enforcement arm of the fed. courts: U.S. MARSHALS. It is a bureau within the U.S. Department of Justice, operating under the direction of the Attorney General, but serves as the enforcement arm of the United States federal courts to ensure the effective operation of the judiciary and integrity of the Constitution.
The URALS are a mountain range that runs approximately from north to south through western Russia, from the coast of the Arctic Ocean to the river Ural and northwestern Kazakhstan. The mountain range forms part of the conventional boundary between the regions of Europe and Asia.24 A. Streaming service whose logo ends with a math symbol: APPLE TV PLUS. A streaming device for Apple devices, smart TVs and more. It features new, original programming every month.
The ALPS are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately 1,200 km across eight Alpine countries: France, Switzerland, Monaco, Italy, Liechtenstein, Austria, Germany, and Slovenia.
48 A. "What I Like About You" co-star: AMANDA BYNES. [b. 1986] is an American actress. She is best known for her work in television and film throughout the 1990s and 2000s.
The ANDES, running along South America's western side, is among the world's longest mountain ranges. Its varied terrain encompasses glaciers, volcanoes, grassland, desert, lakes and forest. The mountains shelter pre-Columbian archaeological sites and wildlife including chinchillas and condors. From Venezuela in the north, the range passes through Colombia, Ecuador, Peru, Bolivia, Argentina and Chile.
58 A. Family CBS series set on a self-named mountain: THE WALTONS. The life of a Depression-era family in Virginia's Blue Ridge Mountains is the subject of this wholesome series. The show is seen from the point of view of eldest son John Boy, who eventually goes to college, serves in World War II and becomes a novelist.
The TETONS are located in Wyoming, and are a sub-range of the Rockies. I once read a quip that only a French man would look at these peaks and be reminded of his mistress's bosom.
Hi, Gang - JazzBumpa here to lead this expedition. No Himalayas, so we won't need a Sherpa guide. Let's get our climbing boots on a start the ascent.
Across:
1. "Sleepy Hollow" actress Christina: RICCI. [b 1980] is an American actress. She is known for playing unconventional characters with a dark edge.6. Scenic overlook offering: VIEW. As of, free, those grand Tetons.
10. Tools with teeth: SAWS. Pliers have jaws.
14. Broadcast warning sign: ON AIR. Admonition to avoid making vagrant sounds.
15. Included in the email loop, briefly: CCED. indicating those who are also sent a copy.
16. See 19-Across: CLEF. I've been playing since 1960, and still want to spell this word with 2 f's.
19. With 16-Across, staff symbol for viola music: ALTO. Presumably, this abomination exists to avoid the use of ledger lines. In reality, there is no rational excuse for it. /rant
20. Oopsy on the keys: TYPO. I love the German word for this: Fingerfehler.
21. Feel out of sorts: AIL.
22. Somali-born supermodel: IMAN. Iman Abdulmajid [b 1955] is a Somali-American fashion model, actress and entrepreneur. A muse of the designers Gianni Versace, Thierry Mugler, Calvin Klein, Donna Karan and Yves Saint Laurent, she is also noted for her philanthropic work. She is the widow of English rock musician David Bowie, whom she married in 1992.
23. 67.5 deg.: ENE. The direction East-northeast.
28. Curtain material: SCRIM. A woven material, either finely woven lightweight fabric widely used in theatre, or a heavy, coarse woven material used for reinforcement in both building and canvasmaking.
30. Vegas opening?: VEE. A spelt-out letter. Meh!
31. "How We Do (Party)" singer Rita: ORA. [b 1990] About whom I know nothing.
36. Technical sch.: INSTitute.
40. Works with hide: TANS.
41. "This tastes awful!": I HATE IT.
42. CPR provider: EMT. Emergency Medical Technician.
43. Darth, as a youth: ANI. Anakin Skywalker.
44. Green stuff: DOUGH. Money
53. In favor of: PRO. As opposed to Anti
54. Sciences partner: ARTS.
55. "I do not see why I should __ turn back": Frost: E'ER. Ever, metrically force-fit.
57. Paris gal pal: AMIE.
61. Prejudice: BIAS. pre-existimng attitude pro or anti some person or thing.
62. Pole at sea: MAST. Support for the ship's riggings.
63. Undercut: ERODE. A gradual wearing away, as by wind or water. Undercut does not strike me as a good fit.
64. Is too busy, say: CANT. Is unable or unwilling.
65. Texter's disclaimer, briefly: IMHO. In My Humble Opinion.
66. Change: ALTER. Typically in a small but significant way.
Down:
1. Google Maps offerings: ROUTES. To get you from point A to point B
2. On the same page: IN SYNC. Synchronized.
3. RV park vehicle: CAMPER. A large motor vehicle with facilities for sleeping and cooking while camping.
4. Vatican farewell: CIAO. Hello or good bye in Italian.
5. Like some bargain bin mdse.: IRR. Irregular - having some small flaw.
6. Blocker in a TV: V-CHIP. A computer chip installed in a television receiver that can be programmed by the user to block or scramble material containing a special code in its signal indicating that it is deemed violent or sexually explicit.
7. "Show your cards": I CALL. To call is to match a bet or match a raise. A betting round ends when all active players have bet an equal amount or everyone folds to a player's bet or raise. If no opponents call a player's bet or raise, the player wins the pot.
8. Sushi bar fare: EEL.
9. Part of wpm: Abbr.: WDS. Words per minute.
10. Rogue: SCAMP. Someone mischievous in an amusing way. Equivalent? I have my doubts.
11. The whole time: ALL ALONG.
12. Professional who breast-feeds another's child: WET NURSE.
13. NorCal airport: SFO. The call letters for San Francisco International Airport.
18. Syrup source: SAP. From maple trees.
22. "__ got it!": IVE. Do you have it?
24. "You said it!": AMEN. Statement of affirmation.
25. The Oscars, say: EVENT. A planned public or social occasion.
26. __ Haute: TERRE. A city in and the county seat of Vigo County, Indiana, United States, only 5 miles east of the state's western border with Illinois. As of the 2010 census, the city had a population of 60,785 and its metropolitan area had a population of 170,943.
27. Grabbed a chair: SAT.
29. Don of talk radio: IMUS. John Donald Imus Jr., [b 1940] also known simply as Imus, was an American radio personality, television show host, recording artist, and author. His radio show Imus in the Morning was aired on various stations and digital platforms nationwide until 2018.
33. Singer Turner's memoir: I TINA. Written in 1986
34. Indian "master": SAHIB. A polite title or form of address for a man.
35. Barcelona aunt: TIA. Spanish
36. Really enjoying: INTO.
37. ABBA musical: MAMMA MIA. A story built around a collection of their songs.
39. Helps: AIDS. Assists
40. __ cozy: TEA. A thick or padded cover placed over a teapot to keep the tea hot.
43. Common online interruptions: ADS. Short for annoyances.
45. Yank from the soil: UPROOT. Violent
46. "Thank U, Next" singer Ariana: GRANDE. Ariana Grande-Butera [b 1993] is an American singer, songwriter and actress. Her music, much of which is based on personal experiences, has been the subject of widespread media attention, while her four-octave vocal range has received critical acclaim.
49. Desert trial: N-TEST. Nuclear bomb explosion carried out in a remote location.
50. "Oy!": YEESH. A non-word, and poor fill.
51. Not familiar with: NEW TO.
52. Big Band __: ERA. A period spanning roughly the mid 3930's to mid 40's, when poplar music was dominated by the big bands of the day.
57. It can replace "pie" in an idiom: ABC. It's just that easy.
58. "Enough!" in texts: TMI. Too Much Information.
59. Bad actor: HAM.
60. Grassy expanse: LEA.