Places like the UK look rather placid and unchanging in many ways compared to say the first half of the 20th century.
If country A wanted country B to do X then it's ability to make it happen through violence will be limited by the willingness of citizens of country A to let it happen.
That willingness will be affected by by the degree of how "alien" people in country B are to people in country A. TV, internet, increased population movement through technological change[1] and so on will decrease that alienness.
[1] I mean both in terms of technology enabling physical travel of people from A->B and technology making a person's origin less important in where they can live during their lifetimes (for example, a programmer can go to work anywhere there is work - they are not confined by location other than by arbitrary things like visas)