Even before this new record high, in the previous ~15 years the average seemed to be around 75% (±), which seems… high? I would perhaps understand the US public thinking that (some levels of) government being "incompetent", but not corrupt.

By some measure the US does seem to have 'decent' scores for perception of corruption:

* https://en.wikipedia.org/wiki/Corruption_Perceptions_Index

* https://www.transparency.org/en/cpi/2025

Meta: in some ways it seems that the public's perception of government is a bit of a self-fulfilling prophecy. In the US there is a large vein of "government is bad/incompetent/corrupt" and that's apparently what the US often gets. While in (e.g.) Scandinavian countries there appears to be a higher level of trust in government, and the people there tend to elect more competent politicians (?).