There are plenty devices that work well with UT and are available in the US, e.g Google Pixel 3a/3a XL. Mentioned devices still have an Android Kernel and many limitations. Waydroid on the Volla phone isn't stable, Ubports itself mediocre compared to SailfishOS and suffers from competing for developer time over other Linux on Mobile OSses.
You're overestimating the Volla phone and Fairphone, 1st one still doesn't support VoLTE which I heard is essential in the US, 2nd thing isn't even recommended by UT.[1]
Either go with an Xperia + SailfishOS [2] if you want more than a toy or Pinephone + PmOs [3] if you love to tinker on your daily driver. Both have VoLTE support.
1. https://devices.ubuntu-touch.io/
3. https://wiki.postmarketos.org/wiki/PINE64_PinePhone_(pine64-...