Whites are guilty if they don't recognize what their ancestors or predecessors did to the Indians. And what their federal, state, and local governments did to the Indians.
They're also guilty if they don't recognize what they and their fellow citizens are doing to Indians today. Stereotyping them as savages, treating them as mascots, denying them their sovereign rights, continuing to break their lawful treaties, failing to protect their cultural and religious sites, underfunding the government services they depend on, etc.
If you've done any of these things, or voted for politicians who have done them, you can take your share of the blame. We all can, including me.
The Jewish mantra "Never again" could be the Native mantra as well. Americans are responsible for knowing what happened before and making sure it doesn't happen again.
For more on the subject, see Genocide by Any Other Name....