So, what can you really expect in the States? I'll quote PC Magazine's comprehensive September 2020 speed test of the major wireless networks:
AT&T, T-Mobile, and Verizon take very different approaches to 5G. To make a long story short, AT&T 5G right now appears to be essentially worthless. T-Mobile 5G can be a big boost over 4G, but its speeds are only what we'd expect from a good 4G network—it isn't a new experience. Verizon's 5G is often mind-blowing, but very difficult to find.
In other words, if you want to buy an iPhone 12 to get faster speeds than you've ever seen before from a smartphone,
you're wasting your money . You're also throwing your cash away if you want to get one today to "future-proof" your phone for 5G. By the time, if ever, 5G becomes truly valuable--again
except for rural users--you'll be wanting to buy an iPhone 14 or 15.