As a follow-up on this thread: just took a trip to lower Michigan last month, and there was no LTE service found on my Moto X Pure Edition. Worked fine my wife's S7 she uses now.
Calling USCC tech support, I was pushed to level 2 support. The guy I got was trying to tell me since I didn't buy the phone from them they couldn't do anything about it because they don't have all the necessary support files to program the Moto X PE for LTE roaming.
Then I asked for a supervisor and was put on hold for several minutes. Same tech came back on, but his supervisor was going to try to add something to the system to force LTE roaming services on my phone and to try rebooting in 20 minutes.
Turned out the tweak worked, although it took longer than 20 minutes for whatever changes to propagate. The network name now shows "Extended" when receiving a roaming LTE signal rather than showing "US Cellular", which is fine with me.
If you have problems receiving an LTE roaming signal with the Moto X PE (and maybe Z2 and X4?), it may be necessary to be persistent about getting whatever tweak applied to your account to get LTE roaming working properly...