I don't know how much detail they have but yes, insurers in the US do know if you've received a ticket for a moving violation (parking violations are irrelevant).
Many of them use solutions like LexisNexis Risk Solutions (which is like a 3rd party API that can return this data). How LNRS gets the data, I'm not sure.
For example, insurers also get data for stolen vehicles since it affects claims. I know this because in a previous (local government) job, I literally sat on calls about building an integration where we sent license plates of stolen cars (officially reported stolen to the police), if we wrote parking tickets for those cars, since we (another local gov agency) spotted the stolen car.
To me, even though I have strong feelings against privacy and surveillance, this felt like a totally pragmatic (and laser focused, it only affect cars that were currently designated stolen) use of the data.