If I don't care about mmWave. Can I to Canada and buy an unlocked iPhone 14 Pro and use it in the States on ATT or on T-mobile? I really want the physical SIM feature because I travel abroad.
Yes, everything works.
mmWave is nothing but marketing. The average 5G speed in the U.S. is 50-150 Mbps, well under the 3.5 Gbps limit for mid-band 5G.