Well... Interesting debate...
I'd like to add my 2 cents.
My opinion (mine, me, I and all that, so not an absolute truth, just the way I see things, YMMV).
It seems like:
1) people in general (not just americans) take the planet and what it provides for granted, that we can simply take and take, and put out all the crap we want to and it won't make any difference whatsoever.
2) many people in general (again, no group in particular, although you should try living in Paris, FR... Probably all very large cities have that though) have a very self-centered outlook. In the sense that, it doesn't matter if what me do now has consequences in the future, as long as it doesn't have an immediate impact on me/my life or the way that I do things, it's OK.
Some people (me included), feel it would be better if people just looked after their own crap, made a slight effort to polute a bit less, and take initiative in that respect. Others feel it is not their place to do so, but that such things should be looked after by the powers that be. Worse still (my opinion again), some others think that the powers that be are doing a good job.
I can't really explain why I have that sense of responsability towards my environnement, maybe that way I was brought up or something, although I'm not an outdoors kinda guy or anything like that, it just seems logical to me.
That's about it I guess... Have to work now.
My 2 cents, make of it what you will.