With the amount of bureaucracy surrounding telecommunications networks in the US, its excessively hard to imagine how this problem just popped up all of a sudden.
It didn't. There's actually a generous guard band between the radar altimeter frequencies and 5G. I say generous because it's more than double what the manufacturers asked for. And what other countries are already providing without issue.
Huh 5G is already massive in China. Haven't heard about 5G and airline issue there.
I think in China it is not as close: 3.5 - 3.6GHz and 4.8 - 4.9GHz. In the US the concern is 3.7-3.98 GHz. Radar altimeter operates within n 4.2–4.4GHz.