It looks like you really don't have any GSM900 operator in the US
However, it looks like you have Sprint on LTE800. It seems to be their only low frequency for LTE, which could be good news since it might mean they are relying heavily on it for 4G coverage. However, I think the Pyra module doesn't do VoLTE (4G voice over IP), meaning for phone calls we're likely to do a CSFB (circuit switch fall back). This requires 2G or 3G access to establish a voice call. This won't be possible with Sprint's GSM and WCDMA frequencies.
And having traveled quite a bit, I can tell you the PLS8-E will be usable in almost all of Europe, Africa, Asia. It really is the "most-worldwide" option for LTE.