There is not really a concern with any country “dumping” bonds.
China would take an increasing loss the more they tried to get rid of, and the US can simply raise it’s provided interest rate a bit through the ordeal to continue to sell new bonds.
Then the interest rates would go down, once parity was again found.
“China would take an increasing loss the more they tried to get rid of...”
Cutting off their nose to spite their face.
Actually, I’d buy bonds once they’ve driven the price down with their sell-off.