[pvaldes]

China will happily jump to help.

To help themselves to be able to track the movements of US nuclear submarines anywhere in waters close to Oregon, Washington or Alaska (Or to move their own submarines freely by the area without telling to anybody except them).

Dismantling sensors around Alaska helps Russia on an hypothetical future attempt to retake the area; and doing it around "51 state" or Greenland is the same thing for US.