"To affirm that Mary's 'no' would halt the plan of salvation is a denial of the sovereignty of God."
Jesus is God's salvation. Without Mary's "yes," we would not have Jesus. Do you have trouble understanding that?
"Without Mary's "yes," we would not have Jesus. Do you have trouble understanding that?"
If we did not have "Mary" we would have had a "Hannah" or a "Sarah" or someone else. Mary could not prevent the salvation of mankind.
There is no one among all the inhabitants of the earth who can "stay His hand". No human can prevent God from fulfilling His plan.