Strangers and aliens - but which kind?
So you get to be a citizen of the earth and fit right in, so long as you're comfortable being alien to God, or you're a citizen and one of God's household, and then you are a stranger and an exile in the world.
None of us likes to be an outsider, so we'd all like to be at home everywhere. Dual citizenship is possible in this world. For instance, it's pretty easy, if an American marries a Brazilian, to be a citizen of both countries.
You can even be a citizen of God's kingdom and a Roman citizen, as Paul was, and so I can be an American citizen and still be faithful to God. I can, without mental reservation, undertake to defend the Constitution of the United States, not because it's perfect, but "the shields of the earth belong to God," and it is far better than nothing. Since God is not unjust or cruel to the United States or any nation, and seeks their welfare by offering them mercy and truth, then if I follow God faithfully, the United Staes will never have a legitimate complaint against me.
But if I'm going to be a citizen of heaven, my rule has to be, "What does the Lord require of you, O man, but to do justice, love mercy, and walk humbly with your God?" And that's not the rule of the nations, whose rule is, "What will we eat, what will we drink, what will we wear" - justice, mercy, and humility be damned if they appear to get in the way.
So who will we choose to be estranged from? Working out that question is the task of the Christian life, which doesn't even start until we actually get started on it. If we work it out right, the world, whatever aspect of it we belong to, will not love us.
Most religion is about asking Jesus into your heart, or performing mizvot, or doing prayers and charity and pilgrimage, and many other worthwhile things, thus presumably being right with God while continuing to fit right into this world.. Jesus put a lot of emphasis into teaching that this is just not possible, so religion saw to it that Jesus was nailed onto a cross - and it is still that way. It's a hard lesson: we're strangers and aliens to God, or we're strangers and aliens to this world.