I would say that American Christians care very much for the environment. I guess I'd want to know where you get the idea that we don't. I'm on an email list for the Evangelical Environmental Network (
http://www.creationcare.org).
In Genesis 1.28, humans are given responsibility to care for the planet as God would. In the days of the ancient Near East, what is expected of the king is responsibility care over that which he rules. The humans are here being mandated with the function of God's co-regents, not only ruling as He would rule, but also as stewards over the earth.
It's both a scientific mandate and an environmental one. We are to learn as much as we can of the natural world so we can intervene in and manage it. It implies a degree of control and direction over nature to regulate its natural forces to advance civilization while responsibly managing its beauty and resources. The Bible is clear that the Earth still belongs to God; we don't own it. In a sense we have it on loan, and are expected to manage it on behalf of its true owner as He Himself would manage it. We have a responsibility to manage the environment and to protect it. Abuse of nature for our comfort is not a right or an option. But neither are we just at the mercy of nature. We are expected to make wise decisions in finding the balance for beauty, protection, survival, and taming its potential for destruction to reduce suffering.
Do these thoughts appear anywhere else in the Bible? The same ideas appear in Ps. 8.6-8. Psalm 100 reminds us that the earth belongs to God. Matthew 6.26 speaks of God's watchful eye over creation. Genesis 2.15 suggest that we rule and subdue the earth by carefully tending it.
The Christian theology of nature is that nature has value in itself. It's not just a resource, a weapon, or a home. What God has made we, who are also his created beings, must not abuse and despise. Nature has intrinsic value because God made it, ordered to function as his temple and for our survival and beauty, and because it reveals God to us in its complexity, balance, order, purpose, beauty, and regularity.