Truly, it's cultural irresponsibility - a consequence of the "powers-that-be" (particularly corporate power; military, manufacturing, and energy) upon the American economic, and government systems - ultimately policy-making decisions - and so much more. It's a consequence of Capitalism's (read: neo-liberal, Chicago-school, economic policies) rather irresponsible application of THEIR mal-directed ideals (except for themselves) upon a public with no sense of history, except in the most formulated sense which supports and reinforces the power structure. The country is divided from itself through naive ignorance and will have trouble making any significant changes that benefit it and much of the world that it controls and has significant influence, which is appears to be diminishing, fortunately.
The sum effects of this program of 'dumbing-down of America' are a reduction in regular and reliable information for ordinary citizens with which to make decisions, an educational reduction in critical logic skills which prohibits clear thinking, a poor understanding of the USA's role and relationship to foreign countries which is a consequence of a brutally aggressive empire-building and maintenance policy and has killed millions in the last 50 years (almost unknown in the USA - surprised?), a truly poor understanding of democracy and how it is distorted by too-strong corporate interests, etc. The list is long. Among these consequences (to answer your question) are a wide range of issues including enormous quantities of research that indicate that human-caused CO2 emissions can cause, or will cause, climate change...and are strongly denied and argued against, as you say. This should be expected. For the most part they American argue self-preservation instead of what would, or should, be argument for planetary preservation. Again, they are not able to think beyond their own borders because there is nothing to need to know beyond their borders.
---------
What is needed, immediately, is a economic and cultural revolution in the USA - not just for it's own salvation, but for the rest of the world, too. - - I am not optimistic. Greed, power, and the ever-present selfishness of human nature are never easy to restrain except in times of crisis - and that point hasn't been reached yet, while others can justifiably say that many are working TOWARDS. I think it's all to late, really. Those in power are too powerful to restrain without full rebellion/revolution, and that just isn't going to happen where it's needed most - in the good, 'ol USofA.
----------------
(Some of these thoughts, (definitely not the last) come from Jarred Diamond's books, any of which I recommend highly. Start with Collapse which documents many, many cultures and civilizations around the world whose demise was caused by environmental degradation. There are some really good success stories, as well, so HOPE does remain - but I have my strong doubts with American leadership.)