This assumes that the telecom carriers and/or the suppliers of the
carrier grade equipment would cooperate with the nation-states in
question. That could happen, certainly, but it becomes much more
difficult to do this surreptitiously.
It is also fairly easy for OS conscious applications to use channel binding
schemes and detect the MITM. At that point, the spies have to move from covert
monitoring to overt surveillance, which should have some noticeable political
consequences.
-- Christian Huitema