Global MIFI / wifihotspot for UK/USA LTE use

Looking for a global Mifi /wifi hotspot. Problem is most work in either USA or UK and not both due to the LTE bands. I could manage with Tmobile AWS UTMS and UK LTE bands (3 and 20) but prefer a full range of UK and US LTE bands (2,3,4,12, 17,20, 30). Anything out there??

I have a Nexus 5X which will work for LTE for both. Any advantage of using a mifi other than the battery drain? The nexus 5x battery is pretty bad. I suppose I could get an external pack for it as an alternative.

One advantage of using a phone as a hotspot is that you can set a data cutoff threshold.

None of the hotspots I own offer that. They have a warning beep (that I never seem to hear) but no absolute cutoff.

The GSM Mifi does have a cutoff feature.

I have two GSM MiFis and all I see is a usage alert that can be set.

Ah... ok, so just alert.

I always feel a lot more comfortable tethering from a phone with a hard cutoff configured.