"'Many times I struck your gardens and vineyards, destroying them with blight and mildew. Locusts devoured your fig and olive trees, yet you have not returned to me,' declares the Lord." NIV translation
Although it seems like Satan has control of things in this world, the devil still has to get authorization from God to do his work. God points out the fact that He had removed His hand of protection from the people and allowed their crops to be decimated. This is a reminder that the only restraint on evil in this world is the very hand of God. When He allows these things, it is for the purpose of drawing people to Him so that they can be saved from an eternal fate that is worse than this.
Here, the Israelites are reminded of what happens when the favor of God is removed from a nation. Their armies were not able to even keep what they had won in previous battles. It seems that, more than ever, nations are putting their trust in weapons of war without remembering that they are useless without the favor of God.
"'I overthrew some of you as I overthrew Sodom and Gomorrah. You were like a burning stick snatched from the fire, yet you have not returned to me,' declares the Lord." NIV translation
Just as with Lot and his family escaping from Sodom, God preserved a remnant through the judgment. The people knew of this story but even so did not repent. The same type of thing will happen again with the 144,00 witnesses in the tribulation.
"'Therefore this is what I will do to you, Israel, and because I will do this to you, Israel, prepare to meet your God.'" NIV translation
Israel was given a period of time where they had the opportunity to repent. Since they did not, they were told to prepare for the judgment of God. For those who do not repent and accept Jesus, the phrase "prepare to meet your God" are the most terrifying words that there can be. We all must ask ourselves if we are prepared and the only way to be ready is by faith in the blood of Jesus Christ.
"He who forms the mountains, who creates the wind, and who reveals his thoughts to mankind, who turns dawn to darkness, and treads on the heights of the earth - The Lord God almighty is his name." NIV translation
The prophet, Amos, goes on to describe who God is. In Hebrew, the name God Almighty is El Shaddai which describes an all sufficient God. El comes from the root word that means power or strength and Shad means breast in Hebrew. Like a nursing mother provides for her child, El Shaddai speaks of the fact that God is all powerful and able to provide for His people. He created all things and so is the rightful owner of all things. In this case, it also speaks of the fact that God controls the times and can decide when the time for repentance is past and judgment is to begin.