The earliest CRTs used in TV (1929-32) were electrostatic deflection, had small screen sizes (3-5 inches), and very low deflection angles.
Early magnetic deflection tubes, developed about 1936-37 and later manufactured as the 9AP4 and 12AP4 had deflection angles of about 35 degrees. This made the tube very long, and it was mounted vertically to keep the cabinet from being too deep in the 12 inch sets sold by all US manufacturers:
http://www.earlytelevision.org/rca_trk12.html
http://www.earlytelevision.org/ge_90.html
By 1939 the British had developed much shorter tubes, with deflection angles of about 50 degrees. These tubes were mounted horizontally:
http://www.earlytelevision.org/baird_t18c.html
This page shows the 12AP4, along with the British CRM-121, one of the 50 degree tubes.
http://www.earlytelevision.org/crt_collection.html
Clearly RCA was aware of the shorter tubes available in Britain, but their interest was getting sets to market to test the public's response. If the war hadn't interrupted TV development, I'm sure RCA would have designed a shorter tube for their next generation of sets.
The most advanced prewar CRT was made by the Germans for their E1. It was rectangular and had a wide deflection angle:
http://www.earlytelevision.org/e1.html