How is ‘the world’ in us? The short answer is twofold.
First, we are born into the world so it is all we know until we are spiritually born and renewed. Romans 12:2 calls us to be transforming by the renewing of our minds. Romans 8 calls us to walk/live in the Holy Spirit. 1 Corinthians 2 informs us we can have the faculty to distinguish between Godly wisdom, demonic wisdom and human wisdom. Until the Holy Spirit works in us, we know nothing else but ‘the world.’
Second, ‘the world’ is in us through the flesh—lust of the flesh (1 John 2:16). But what is the flesh? This is a difficult question for several reasons. Even though attributes of the flesh are given in Galatians 5:19-21, there are physical bodily elements and soulish elements so exactly how we distinguish our soulish elements from holy and defiled, fleshly, carnal, old self, etc. takes effort.
Thirdly, who in the American church teaches it? I haven’t heard any detailed teachings. The reason I know about it is because of 12 step programs, which focus on the ‘addict’, alcoholic, etc., which are expressions of the flesh. — yet everyone lives in it.
Rich, capitalist America permeates our societal order. The flesh, in its hedonistic forms, dominates: pleasure in the popular realm, power in the political, covetousness in the economic. We swim in it like fish in water, rarely stopping to ask what the water actually is.
Lord, reveal to me the flesh I swim in without thinking. Teach me to walk in the Spirit and think with kingdom wisdom. Help me see the world’s grip on my heart — in pleasure, power, and greed — and by Your Spirit, be set free. May I not love the world or anything in it, but find my satisfaction in You alone.