  This Snowmass21 Contributed Paper encourages the Particle Physics community
in fostering R&D in Superconducting Nb3Sn coated Copper RF Cavities instead of
costly bulk Niobium. It describes the pressing need to devote effort in this
direction, which would deliver higher gradient and higher temperature of
operation and reduce the overall capital and operational costs of any future
collider. It is unlikely that an ILC will be built in the next ten years with
Nb as one of the main cost drivers of SRFs. This paper provides strong
arguments on the benefits of using this time for R&D on producing Nb3Sn on
inexpensive and thermally efficient metals such as Cu or bronze, while pursuing
in parallel the novel U.S. concept of parallel-feed RF accelerator structures.
A technology that synergistically uses both of these advanced tools would make
an ILC or equivalent machines more affordable and more likely to be built. Such
a successful enterprise would readily apply to other HEP accelerators, for
instance a Muon Collider, and to accelerators beyond HEP. We present and assess
current efforts in the U.S. on the novel concept of parallel-feed RF
accelerator structures, and in the U.S. and abroad in producing Nb3Sn films on
either Cu or bronze despite minimal funding.
