There are a variety of examples but the most recent ones relate to high profile pipeline protests. These protests have by and large been about and on land that was illegally annexed. These lands are by and large guaranteed by treaties that have since been illegally broken. Militarized forces from private security forces to federal agencies have been involved in the suppression.
https://en.wikipedia.org/wiki/Dakota_Access_Pipeline_protest...
Less recent examples include the violence surrounding the AIM movement in the early 60s and 70s. Protesters have been unjustly imprisoned for decades. There was violence from federal agencies on multiple occasions throughout the time period when AIM was most unified and active.
https://en.wikipedia.org/wiki/American_Indian_Movement
Shockingly to many people forced sterilization continued well into the 70s as well, which fits the definition of attempted genocide.
https://en.wikipedia.org/wiki/Sterilization_of_Native_Americ...
There are more examples but these are the most documented and high profile.
It is a social war more than a material one. Residential school policy is an example of this. You may have heard the phrase "kill the indian, save the man". This is a policy of longterm cultural genocide and erasure.
Edit: I also forgot to mention another example which is the passive acceptance of the very high rates of missing and murdered indigenous women. The lack of investigation from federal authorities who are supposed to have jurisdiction over these things implies tacit acceptance of the systematic murder of vulnerable indigenous people.
https://mmiwusa.org/