The issue is that the global diet for treasuries artificially holds down interest rates. If purchases slowed or holdings were sold, interest rates would rise. Whether it would be a crisis or merely hurt is a marginal distinction.
The government of the USA would go bankrupt in months if interest rates rose to 5%, which is an historically normal figure.
There's nothing artificial about it. That's normal economics at work.
Interest rates will remain low as long as the economy remains weak. They will rise to 5% when the economy becomes stronger and inflation rises, reducing the level of existing debt to GDP.
The government of the USA would go bankrupt in months if interest rates rose to 5%, which is an historically normal figure.