We purchased our American made squirrel proof bird feeder from the following company: https://www.rollerfeeder.com
We love watching the many different birds flock to our bird feeder, we also love the occasional “flying” squirrel who tries to outsmart the bird feeder. When we first put it up, it took a couple months for the birds to find it so the squirrels had a lot of practice in the beginning, now they mostly eat whatever the birds drop.