Is James 5:13 basically saying that nothing is too difficult for the Lord to handle?
In a sense, yes. But this verse and the following ones show that we can communicate with God no matter the situation. If people are suffering in trial, pain, and persecution, they can cry out to God and he hears and answers.
The total opposite is the state of the believer who experiences cheer, victory, and happiness. Praising God is, another form of prayer. Prayer is talking to God, communicating with him. We can communicate just as much and what we think of prayer and what we call praise.
James probably points out these two extremes show that every state of the believer in between is also a time to turn to God. Whether we feel we are experiencing his great blessings or the trials of life, God is one prayer away.
We must learn to turn to him in every situation. We must not forget him in blessings, or credit ourselves with working for those blessings. But we must not forget him in our sufferings and turn to our own resources. In every situation, God is always there.
James continues to ask in the next verse (James 5:14) if anyone is sick. The whole book of James is about how God helps us in also works of trials. Even the situation of sickness, James calls people to ask the elders, people full of faith, to pray the prayer of faith (James 5:15).
James even goes so far as to include people who have sinned against God as part of the process of healing them from sickness (James 5:15). Now there’s a whole theology of sin and sickness being tied together throughout the New Testament, but needless to say James runs the whole gamut of states of the believer.
In every one of these states, calling out to God in prayer should be our natural response. God can do all things, so in all things we cry out to him. We seek his intervention, his blessing, his healing, and he can do all these things.