The US government probably seems less corrupt than the EU because of its laid back approach to a lot of policies. However, that's exactly the type of corruption that a lot of people are talking about.
The country needs a lot of change to tackle big problems like climate change and increasing wealth inequality however the government is sitting back doing nothing because many representatives are lobbied by big interests to let the big interests continue doing what they're doing.
Over the last few years it's become increasingly clear that many people don't think for themselves and will believe in whatever their favorite media tells them. A lot can be done to convince the population that climate change and income inequality aren't major issues.
Also, that poll seems flawed because it asks a superlative question (what is the "most" important problem) instead of using something like ranked choice where perhaps climate change and income inequality were everyone's second and third options.
The country needs a lot of change to tackle big problems like climate change and increasing wealth inequality however the government is sitting back doing nothing because many representatives are lobbied by big interests to let the big interests continue doing what they're doing.