The Son of God said, "My Kingdom is not of this world". So when we pray for the coming of the Kingdom, what are we asking for?
Certainly, the world today seems as far from God's Kingdom as we can get. Secularism is triumphing, Catholics seem to be one of the few minorities people are allowed (sometimes even encouraged) to discriminate against, and God is banished from all serious debate.
How can we build God's Kingdom here on Earth when we are surrounded by hatred and violent images, when our television and cinemas are dominated by violence, pornography and blasphemy, when innocent children are being killed in the name of choice, when the authorities are so anxious that we should not cause offence to non-believers that Christmas celebrations are renamed Winterval and people are banned from wearing crucifixes in schools and at work, when the image of the Church is so tarnished by the prejudiced ramblings of the liberal media, when greed is glorified and modesty ridiculed?
But are we praying for God's Kingdom to be built on Earth at all? "My Kingdom is not of this world" - are we rather praying for the grace to join Him in His Heavenly Kingdom? And is the coming of the Kingdom a gathering of faithful souls around the Lord in His Heavenly Kingdom?
The Catechism tells us that at the end of time, the Kingdom of God will come in its fullness. The universe will be renewed, and there will be a new Heaven and a new Earth.
"Far from diminishing our concern to develop this earth, the expectancy of a new earth should spur us on, for it is here that the body of a new human family grows, foreshadowing in some way the age which is to come. That is why, although we must be careful to distinguish earthly progress clearly from the increase of the kingdom of Christ, such progress is of vital concern to the kingdom of God, insofar as it can contribute to the better ordering of human society." (1049)
So we're not building an earthly kingdom or plotting an earthly revolution, but as we attempt to do God's will and grow in our love for Him, we are spurred on by the expectation of what is to come, and inspired to contribute in our small way to the progress of society towards this glorious end. And as we grow in our love for Him, He is enthroned in our hearts.