I don't think he could make that claim as Carlos II, the Spanish Monarch whose deathbed will made Louis XIV's grandson Phillip V, King of Spain; had clearly stated that the Kingdom's of Spain and France could not be united; that if Phillip claimed the Spanish throne, he and his heirs must give up any claim to the French throne. So it would be difficult to imagine Louis XIV making any bid that God would be angered that the thrones were not united.

The whole War of Spanish Succession could have been avoided if all the parties had just respected the Last Will and Testament of Carlos II to begin with; in fact England and the Dutch Republic were prepared to do just so; but the Parlament de Paris rejected the stipulation that Phillip could not inherit the French throne upon Louis XIV's death and so war the Grand Alliance of the Hapsburg Empire, Dutch Republic, England, and Savoy came together again to oppose the French in their ambitions.

By the end of the war all sides were looking for peace. The Treaty of Utrecht was not Louis XIV's first attempt to bring the war to an end; in fact as early as 1706 he had been attempting to find a peaceful settlement; he was even prepared to give up any claim to the Spanish throne in order to keep control over the Dukedom of Lorraine and the parts of the Spanish Low Countries he had effective control over. However, the Grand Alliance preferred to push the advantage they had gained with their victory over the French at the battle of Blenheim and the war essentially ground to a stalemate for the next five years.

In 1709 Louis would again start the peace process; things had continued to sour for the French- terrible weather had lead to harvest failures in 1709 and people were starving to death or succumbing to diseases because they were so malnourished. Louis again proposed to give up the claim to Spain; this time offering to also give up Strasbourg, Low Countries, and formally recognize Queen Anne as the legitimate ruler in England (instead of the exiled James III). The Grand Alliance counter proposes, agreeing to what has been offered, but further demanding that Louis XIV help remove his grandson in Spain and pay for the war effort their. Louis XIV rejects these terms and the war continues with further crop failures and starvation in 1710. However; the French begin to turn the tide and the already slow advance of the Grand Alliance grinds to a halt; England and the Dutch are both ready for peace and when the Hapsburg Holy Roman Emperor Joseph I dies in 1711, peace is given a chance. Everyone is tired of fighting and at that point none of them want Archduke Charles- the soon to be crowned Holy Roman Emperor, to also inherit Spain- which had originally been the objective of the Grand Alliance.

So why didn't Louis just renege on the Treaty of Utrecht? At that point he was just glad for the War of Spanish Succession to be over. He had been trying for 7 years to find a way out of the war and had been unsuccessful.

No doubt worth keeping in mind that this was the third major war Louis XIV had engaged in. These wars had ultimately left France with few territorial gains and heavy loss of life and money. The wars had left parts of the French economy in ruins and the people were increasingly chaffing under the taxes that were being raised.

• War of Devolution 1672-1679
• The Nine Years War 1688-1697
• War of Spanish Succession 1701-1714

So no, no one wanted to go back to war at that point. The wars had drained the nations pretty dry and hadn't seemed to accomplish much in the end. No matter how great the gains early on in the war, ultimately, it came to nothing.

A united France and Spain was the worst nightmare of most of Europe, especially France's two traditional foes - the English/British and the Hapsburg domains. France alone was the dominant force on the continent at the time - a highly centralized state with one of the best and largest armies in Europe, having defeated the Spanish Tercio at Rocroi in 1643 - and combined with Spain's possessions in the Americas, the Netherlands, and Italy, they would be ridiculous.

France had been an enemy of the Netherlands since the mid-17th century; the Franco-Dutch War, also fought by Louis XIV, was a very recent example of this. Louis' nemesis at the time had been William of the House of Orange, stadholder of the Dutch Republic. So when Protestant William became William III, King of England and later Great Britain, the animosity Louis had for him only added fuel to the always-ready Anglo-French fire. The dynastic change removed the Catholic Stuarts, which had traditionally been quite friendly to France. (Yes, the Protestant-Catholic divide was still a big deal in the late 17th Century.)

That aligned the Dutch and the British against a powerful French state. The Hapsburg domains (mainly consisting of Austria, Bohemia, and Hungary) had long had a dynastic feud with France over southern Germany and Italy, going back to the late Middle Ages. They were the two contenders for the resident power in continental Europe, and currently France was winning. The Austrian Hapsburgs also had major beef with the whole "Bourbon Spain" deal because Louis' nephew stood to succeed a Hapsburg, and the Austrian Hapsburgs had eyes on lands in Italy like Lombardy. They were territories the Austrians felt rightly belonged to them.

So, you have three major powers - Britain, the Dutch, and the Hapsburgs - who have major reasons not to want to see a mega-France under the Bourbon dynasty.

In the War of the Spanish Succession, 1701-1714, these countries formed the "Grand Alliance" in a bid to keep Louis XIV from uniting the thrones. Officially, Louis had promised in the Treaty of Ryswick not to unite the thrones, but he had already violated numerous provisions of the treaty (including occupying several border forts in the Spanish Netherlands) and this put the Grand Alliance on its guard.

This is a very interesting war, but to spare the gory details the Allies were on the verge of winning before the Hapsburgs decided they wanted to have their cake and eat it too, pushing for their own candidate to be put on the Spanish throne. This alerted the British and Dutch to the possibility of a super-Hapsburg state, which sounded almost as bad as a super-France. The Brits and Dutch seriously eased up on the war effort, which allowed France to turn the war around a bit.

In the peace treaties of 1713-1714, referred to as the Peace of Utrecht, Louis' nephew Philip was confirmed as King of Spain on the conditions that the thrones never be united. (Had Louis won a major victory in the war, that might well have been different.) In return, Britain received Gibraltar in southern Spain, and parts of French Canada, and Austria received the Spanish possessions in the Netherlands and Italy.

Basically, it was a compromise. A peace was brokered to keep the balance of power from tilting out of control. Technically, the French came out on top, but they were not united with Spain (hell, they were at war four years later after Louis XIV died, because Philip tried to claim the French throne) and Spain's power was severely reduced in Europe.

To answer your questions specifically:

The concerns of outside powers kept Louis XIV from uniting France and Spain. They would've been right back at it, and it was only the fact that the Grand Alliance couldn't get along that kept them from pushing the war farther. If Louis had tried it again, they'd be right back at it again; nobody wanted mega-France around. It would be like the West's reaction today if Russia and China tried to unite, and China owned Japan.

He could've, but that really wouldn't have stopped the Grand Alliance from forming. (Britain and the Dutch were Protestant after all.)

The armies were small armies full of professionals; especially at this point, they did what the royals told them. And a super-France was very much worth preventing; it would dominate England/Britain navally, crush the Dutch, and defeat Austria on land through sheer power.

Basically, Louis XIV wasn't making decisions in a vacuum. Violation of a treaty was plenty of reason to go to war, and many nations of Europe were willing to intervene to stop the union of France and Spain.

Side note: The reason I refer to England/Britain is that the separate kingdoms of England and Scotland became the United Kingdom of Great Britain in 1707, the middle of the time period I refer to in general terms.

Source:

Marlborough by Angus Konstam, Osprey, 2010

The Age of Battles by Russell Weigley, Indiana Univ. Press, 1991