In Shakespeare's Henry V, what is the bill that Ely and Canterbury are talking about, and why are they against it? In what way is Henry dependent on the church?

In Act 1, Scene 1, the Archbishop of Canterbury and the Bishop of Ely are discussing an old bill that has resurfaced in King Henry's court. Both the Archbishop and the Bishop are against this bill because it will reduce their land holdings and overall wealth.
Essentially, if the bill passes, all the land that "devout" men have bequeathed to the church will be confiscated and appropriated for the king's use. The confiscated wealth will allow the king to maintain fifteen earls, fifteen hundred knights, and six thousand two hundred squires.
Aside from this, the lepers, the aged, and the poor will be "well supplied" with their needs from this confiscated treasury. To add insult to injury, the Archbishop maintains that the bill provides for a yearly sum of a thousand pounds to be paid into the king's coffers. This will, in all effect, dilute the Church's wealth, power, and political influence; so, the Archbishop and the Bishop are against the bill.
The Bishop of Ely questions whether King Henry is amenable to what the House of Commons proposes, and the Archbishop confides in him that he's already proposed a way to thwart the king's purposes. Essentially, the Archbishop has offered Henry more money than the Church has ever given any of his predecessors. He means to tempt Henry with financial support from the Church to bolster Henry's claim to the throne of France. With Henry thus occupied, the king will have no reason to confiscate the Church's property.
When the two clerics later meet with King Henry, the Archbishop and Bishop reassure the monarch that there is no valid legal obstacle to thwart his claim to the French throne. They flatter him and tell him that he is "in the very May-morn of his youth, / Ripe for exploits and mighty enterprises." Upon hearing this, Henry is persuaded that he does indeed deserve the French throne and that he can mount a military campaign successfully.
We must remember that Henry is dependent upon the Church for its material and social support in his campaign to take back the throne of France.
Without the Church's coffers, Henry cannot mount a successful military campaign on two fronts. When he invades France, he will also need an army to push back against Scotland (which always attacks when England is at war with another power). Henry is not only dependent on the Church for material support, but he must also rely on the clergy to justify his French invasion to the people. Since the Church's coffers are filled by the populace, the people must be convinced that the king is acting in England's best interests. So, the Church and the king have a precarious relationship that's predicated on the ability of both to leverage wealth and power to protect their political interests.