Why did no one answer: The people did not respond to God's repeated call to trust him and repent of their sins. They were deaf and stubborn (see Isaiah 6:9–10; 29:18; 35:5; 42:18–19).
The Lord came and called the people through the prophets (see also Isaiah 65:1–3).
do I lack the strength to deliver you?: God could rescue Israel and Judah from the Assyrians and Babylonians, but he first had to address his people's sinfulness (see Isaiah 59:1).
My rebuke dries up the sea: This refers to the parting of the Red Sea during the exodus from Egypt (Exodus 14:21–22).