That's not really true, afaict. This press release[1] states that Fab 21 (Arizona) phase 1 is 4nm, which is not the best but clearly is enough to manufacture the A16, phase 2 opening in 2026 will be 3nm, and phase 3 will be 2nm or better. I'm not a semiconductor engineer so maybe there's some process nuance that I don't know, but it certainly seems that this is at or near the top of TSMC's process list.