It's kind of disgraceful that the ships described were sent. The US Navy had many more modern ships then- there were several classes of two-gun turret (with three turrets) destroyers built between the wars, much more modern than the old four stack destroyers, and a couple of 1930s heavy cruisers should have been sent rather than an obsolete light cruiser with one-gun turrets. Jeez.
Squadron 40-T was formed September 17, 1936 with the CL Raleigh (1924) as flag from 9/17/36 to 4/28/1938. The cruiser was coming out of Norfolk Naval Yard after completion of an overhaul 6/15-9/16/36. The ship was available and coming out of overhaul.
As for destroyers, the modern destroyers available were 8 Farragut class and 2 Porter class destroyers. There were others nearing completion or working up/on shakedown cruises. But deployable modern destroyers were 10.
The composition of Squadron 40-T comprised a 12-year old Cl, 2 16-year old DDs, and a 4-year old Coast Guard cutter, The size and composition of the force were based on the mission: "protect US Citizens". The immediately available, freshly overhauled Raleigh was a valid choice. The 4-piper destroyers were representative of the vast majority of US destroyers at the time. And generally, new construction commissioned after formation was used for fleet operations, not distant stations without existing US naval bases..
Once the organization of Squadron 40-T was established in 1936, it was never significantly altered. An Omaha class cruiser was maintained as flagship and 4-piper destroyers as the complement.
Raleigh was the flag to 4/28/38; She was replaced by USS Omaha which served as flag until May, 1939; Trenton became flag in June 1939 thru July 1940. Omaha replaced Trenton in July 1940 thru disbandment of the Squadron on October , 1940.2