>>87906757EN HQ does exist, its just that its in JP, in the same office as JP HQ. Probably some desks clumped together in the office as the EN area.
HoloEN doesn't legally exist. Its an internal branch of Hololive, not its own separate legal entity. The only place where they can hire internal staff is JP.
Cover USA is being set up but afaik its for shipping merch. It'll be cheaper for Cover to use their existing office in JP and pay JP wages.