I think the statement from Representative Joe Barton (R-TX) says everything that could ever be said about the harmful effects of scientific illiteracy on the United States.
Perhaps the most global harmful "thing" is the fact the science deniers and their more generally anti-intellectual and anti-science allies (in the public and in government and in bureaucracies) make claims---rather false statements (such as Barton's) that are patently and obviously lies and disinformation, BUT make these claims (lies and disinformation) in language carefully constructed and deployed to mimic authentic scientific language and speech.
For example: There is now talk of some utter nonsense called "Scientific Creationism".
And so, if we don't know the facts---the data derived from authenticated and peer reviewed and tested research, we are subject to the pseudo-scientific claims of those who co-opt the language of science to, in fact, promote an anti-science message.
We see this deployed very skillfully not only by Evangelical Christians and their right-wing political allies, but also by those who promote such preposterous notions as "ancient alien theory" and "intelligent design".