It is a misconception among some that all non Muslims lands should be attacked. Muslims should only sent missionaries to spread the message of Islam to non Muslim region. That is how Islam spread to countries like India in the first century, not through military movement. 

Muslims can attack a place to liberate a place if the ruler is cruel and the people there are being oppressed 

> And what is [the matter] with you that you fight not in the cause of
> Allāh and [for] the oppressed among men, women, and children who say,
> "Our Lord, take us out of this city of oppressive people and appoint
> for us from Yourself a protector and appoint for us from Yourself a
> helper"? [Quran 4:75][1]

Other than this, there is no point in starting war on peacefully living people. 
> Whenever they kindle the fire of war, Allah puts it out. And they
> strive to spread corruption in the land. And Allah does not like
> corruptors. [Quran 5:64][2]

In modern times, we can see starting war is easy but to stop it is very difficult. All the people including civillian in both sides suffer, all their daily life gets effected by war. So no point in arguing for war, when there is no clear instructions in Quran or Sunna to start war on all non muslim nations. Actually this concept of dar-al-islam(house of Islam) and dar-al-harb(house of war) to denote all non muslim regions, is not from Quran or Sunnah, it is concept created by later scholars.


  [1]: https://quran.com/4/75
  [2]: https://quran.com/en/5/64