Tailscale will enable all of this.

Set up a US device as an exit node, and configure other devices to proxy through it.

Yes, you've described Tailscale + Exit Nodes + Tailnet that you invite your family to. Install Tailscale and enable some devices as exit nodes - it's pretty much as simple as that.

I just use WireGuard to connect my local network. I see no point in throwing a middleman into the mix.

Tailscale is probably what you want, but if you care about privacy you'll have to be sure to disable the telemetry/logging/spying option on each of your nodes.

By default it will leak your so-called “private” network behavior to Tailscale (connections on what port, from what node, to what node, opened when, closed when): https://tailscale.com/docs/features/logging

if you are behind cgnat (both ipv4, ipv6) then vps, have public ipv6 then you can connect via public domain (ddns openwrt) and if you have a public ip, wireguard it is

I found good success with OpenWRT/Tomato and WireGuard.

The interface is bad when it comes to provisioning but it can be done with a QR code and once it works the native experience of turning on the VPN was just stunningly fast. In this day and age you expect things to be slow with negotiation and various unreliable steps but it was just amazing that I tap the VPN button on iOS and it's connected in a fraction of a second.