And yes, salvation first and then living an obedient life in God's will can bring tangible blessings.
And the "Kingdom of God" is at hand as we can see by the end-time prophecies being fulfilled almost on an hourly basis in our generation. As Christians we have a responsibility to spread the Gospel and make as many people as possible aware that Christ is returning soon to, among other things, set up His kingdom.
But nowhere does Jesus say that there will be a literal, physical kingdom set up by human beings and nowhere does Jesus say that we are to work to gain control of the earth's governments and social institutions. Nor does Jesus' return depend on human beings attempting to do any of those things.
“...nowhere does Jesus say that we are to work to gain control of the earth’s governments and social institutions...”
...er, how about: “Go into all the world and preach the gospel to all creation...teaching them to obey all I commanded...” Jesus certainly isn’t saying that He has nothing to say about the poor, the innocent, children, slaves, employers, husbands, wives, kings, government officials, merchants, soldiers, craftsmen, farmers, butchers, bakers, and candlestick makers (oops, got carried away there) but you get the point.