Does denying climate change work similar to believing the earth is flat? I have a vague idea how believing in a flat earth may work. (Not enough to write it down)

But it still irritates me that an appreciable fraction of the general population in the US deny that climate change is caused mainly by human influences. Even more so as it seems to be a fraction large enough to be politically relevant. 

I see that this question has a strong political connotation, which is opinion based. But that is not part of the question.

It is somehow culture-related, as it's different in Europe, at least in Germany. 

I would expect it is a fringe group like people assuming a flat earth.
There is a related, but different kind of group. People denying that the Holocaust happened. This has a strong political association to extreme right groups.

Is assuming flat earth and denying climate change the same kind of phenomenon?
There is serious work on this, despite it being a political minefield. You're probably looking for Lewandowsky, et al. (2015).
If you want to get some distance from the issues of the day (and associated name calling) and into the mechanisms that drive this sort of phenomenon in general you might get more joy out of something like Cook &amp; Lewandowsky (2016).
That will bring you into stuff like Hahn, et al. (2018). That's not directly political at all, but I think the relevance to your question is pretty strong. This is one of those fields that is exploding thanks to ever-better desktop computing, there's a ton of stuff that hasn't been tried yet! Hope you have some fun with it.
References
Cook, J., &amp; Lewandowsky, S. (2016). Rational irrationality: Modeling climate change belief polarization using Bayesian networks. Topics in cognitive science, 8(1), 160-179. doi: 10.1111/tops.12186
Hahn, U., Hansen, J. U., &amp; Olsson, E. J. (2018). Truth tracking performance of social networks: how connectivity and clustering can make groups less competent. Synthese, 1-31. doi: 10.1007/s11229-018-01936-6
Lewandowsky, S., Gignac, G. E., &amp; Oberauer, K. (2015). The robust relationship between conspiracism and denial of (climate) science. Psychological Science, 26(5), 667-670. doi: 10.1177/0956797614568432