Maybe they should just buy plastic eagle feathers from China.
I believe the concept of property ownership was not in place when the bad Europeans arrived and settled the USA. That concept arrived with the Europeans. The settlers brought civilization and government with them and had the power to enforce it. For those that have severe guilt about "taking" the land from the native Americans, you could donate your property to them now and move back to your country/continent of origin. That should relieve your guilt and make everyone happy.