Actually, no it isn't a call to repentance. You need to read the whole passage. God is saying that if ISRAEL is unfaithful and God sends disaster on the country THEN if they repent he will heal their land.

(2 Chronicles 7:11-16 NIV) When Solomon had finished the temple of the LORD and the royal palace, and had succeeded in carrying out all he had in mind to do in the temple of the LORD and in his own palace, {12} the LORD appeared to him at night and said: "I have heard your prayer and have chosen this place for myself as a temple for sacrifices. {13} "When I shut up the heavens so that there is no rain, or command locusts to devour the land or send a plague among my people, {14} if my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then will I hear from heaven and will forgive their sin and will heal their land. {15} Now my eyes will be open and my ears attentive to the prayers offered in this place. {16} I have chosen and consecrated this temple so that my Name may be there forever. My eyes and my heart will always be there.

There's a longer passage in 1 Kings

(1 Kings 8:33-39 NIV) "When your people Israel have been defeated by an enemy because they have sinned against you, and when they turn back to you and confess your name, praying and making supplication to you in this temple, {34} then hear from heaven and forgive the sin of your people Israel and bring them back to the land you gave to their fathers. {35} "When the heavens are shut up and there is no rain because your people have sinned against you, and when they pray toward this place and confess your name and turn from their sin because you have afflicted them, {36} then hear from heaven and forgive the sin of your servants, your people Israel. Teach them the right way to live, and send rain on the land you gave your people for an inheritance. {37} "When famine or plague comes to the land, or blight or mildew, locusts or grasshoppers, or when an enemy besieges them in any of their cities, whatever disaster or disease may come, {38} and when a prayer or plea is made by any of your people Israel--each one aware of the afflictions of his own heart, and spreading out his hands toward this temple-- {39} then hear from heaven, your dwelling place. Forgive and act; deal with each man according to all he does, since you know his heart (for you alone know the hearts of all men),

It should be noted that Americans are not God's people. We're not called by his name. God hasn't punished America for its sins yet. Christians in America have no need to repent if they're already right with God.

2 Chronicles 7:14 is one of the most misapplied verses today. Along with Jeremiah 29:11.