There needs to be a way to have an overlapping template of Theatre/HQ
control on Allied lands. The fact that you cannot makes it very hard to
stage US Forces in the UK from the US.
You cannot, unless you micromanage them, conduct the air bombing campaign
over Germany from the UK. You cannot give them to larger HQ control or its
gonna send em to the Phillipines (always the Phillpines...). You begin to hope
Japan invades there just to close Clark Field! LOL! If you assign them to a
HQ in the US they will not deploy them to the UK they will twidle their thumbs
in the US (or Phillipines) unless you micromanage them.
You need to be able to build airbases in the UK as the US as the UK does
not have enough for the air war over Germany.
You need to be able to put US radar on your airbases (it was portable, not
the huge towers of the 1930s by then).
All this missing makes the UK a place mostly to avoid as you cannot USE the
territory properly as was done. You end up as an unwanted relative soaking
off the family.....