Though the idols cannot save the burdens they try to carry, God can. God carries and God saves.
The promise of Isaiah, son of Amoz, who prophesied in Jerusalem, is included among the prophets of the eighth century B.C.E. (along with Amos, Hosea, and Micah)--preachers who boldly proclaimed God's word of judgment against the economic, social, and religious disorders of their time. More 45:22 falls within a longer argument about who can carry and who can save. The idols cannot; indeed, they themselves must be carried by beasts and cattle (46:1-2). But God can carry and will save (46:3-4).
“Carrying” becomes equivalent to “saving” in this passage. To be saved is to be carried. Throughout the Bible, God is pictured as one who carries–as an eagle (Exodus 19:4), a mother (Isaiah 66:12-13), a shepherd/warrior (40:10-11), a bearer of sin (53:12), even here in this passage as a beast of burden. God carries the people whom God governs on God’s own shoulder (9:6); people and beasts must carry the idols, but God carries all.
The New Testament continues this theme with the announcement of Christ who came to “bear the sins of many” (Hebrews 9:28). German theologian Dietrich Bonhoeffer makes the same point: “God is a God who bears” (Dietrich Bonhoeffer, Discipleship [Minneapolis: Fortress, 2003] 90).