what i know is the B66 LTE frequency which i'm not aware of any NA carrier using this frequency
There are more differences in LTE frequencies than just B66, which is used by AT&T. Possible carrier aggregation combos for LTE-Advanced are different as well.
HTC U11 WHL - North America
2G/2.5G- GSM/GPRS/EDGE
850/900/1800/1900 MHz
3G UMTS
900/850/AWS/1900/2100 (B8/B5/B4/B2/B1 with 900/850/AWS/1900/2100 diversity), HSDPA 42, HSUPA 5.76
4G LTE (up to 600Mbps download speed/with 2CA, 3CA Carrier Aggregation and 256 QAM, service dependent)
FDD: Bands B1/B2/B3/B4/B5/B7/B8/B12/
B13/B17/B20/B25/B26/B28/B66
TDD: Bands B41
VoLTE,Wi-Fi Calling
Cat 16 LTE ready with 4x4MIMO, supports near 1Gbps download speeds and upload speeds of up to 75Mbps
HTC U11 DUGL - EMEA dual-SIM
2G/2.5G - GSM/GPRS/EDGE
850/900/1800/1900 MHz
3G UMTS
800/900/1900/2100 (B5/B8/B2/B1), HSDPA 42, HSUPA 5.76
4G LTE (up to 800Mbps, service dependent)
FDD: Bands B4/B12/B17/B28/B20/B5/B8/B3/B1/B7/B32
TDD: Bands B39/B40/B38/B41
with 2CA, 3CA, 4CA Carrier Aggregation
VoLTE,Wi-Fi Calling
Device capable of support Cat 15 LTE, download up to 800Mbps, upload up to 75 Mbps