#1.   Coordinated structures work better than uncoordinated structures. 

After the American colonies' successful rebellion against Britain in 1781, they formed into an Articles of Confederation.  Unfortunately, this led to chaos as border clashes broke out among the Northern states of New York, Connecticut, and Pennsylvania and each colony had its own currency.  So they unified the structure much more with the Constitutional Convention of 1787.  Then after the Civil War of 1861 to 1865 the United States of America emerged as one country more than ever before.

After the World War of 1914 to 1918, the League of Nations was born thanks to US president Wilson.  But the harsh peace of Versailles imposed on Germany by the fourth ranked power in the world, France, still bitter from the Prussian defeat of 1871, led to another World War.  That plus Wilson's stroke and weak economy after the war from 1919 to 1921 lead to failure of the US to join the new arrangement.

#2.   Direct democracy works better than indirect democracy.

In US history the indirect democracy of appointees running the Articles of Confederation was much weaker than the direct democracy of an elected congress and president in the US Constitution.  Beginning with Oregon in 1906, direct election of US Senators worked better than US Senators appointed by state legislatures.  In 1858 this had led to the appointment of Douglas rather than Lincoln to the US Senate from Illinois.  In 1860 direct election of the US president led to Lincoln defeating Douglas in Illinois as well as nationally.  Today an appointee run United Nations is much weaker that a directly elected European Parliament.

#3.   Too much central power in too few hands is dangerous. 

Dictatorships can go to war much more easily than democracies.  As Rome evolved from a Republic run by the Senate to dictatorship of the Emperors, Rome moved into a period of many civil wars.  As America moved into the quasi empire of the period after World War Two, declarations of war were replaced by resolutions and the imperial presidency emerged as superior to the congress, somewhat like the Roman situation, with many small wars the result.

#4.   League of Nations

Lacking an enforcement mechanism, the League of Nations fell apart in the thirties as Hitler marched Germany into war.  The normal course of history was upset in 1917 when an outside power took the win away from number one European economic power Germany as the war was about to turn in Germany's favor as they defeated Russia and brought the troops on the Eastern front over to the Western front.  Then America stepped in enough to turn the tide and award the victory to number three European economic power France.  France was still embittered by the loss to Prussia almost fifty years before.   Greater economic powers Britain #3 and America #1 allowed the fourth ranked world power France to impose such a harsh treaty on Germany #2 that it bankrupted the Weimar Republic in the twenties and led to Hitler's rise in the thirties and a new war.  No less a figure than the most famous economist of the twentieth century, John Maynard Keynes, on the British negotiating team, wrote a book about how the Versailles Treaty of 1919 would lead to another war.

#5.   United Nations

The United Nations chief asset was the Security Council and its chief flaw the veto of the permanent members.  The indirect appointment by governments of representatives to the United Nations also contributes greatly to its weakness.  These representatives have only secondary authority to represent their peoples, making the United Nations an association of governments rather than a democracy of the world's peoples.  

The UN Security Council was weakened as the moderate Franklin Roosevelt was not there after the war to broker deals between the extremes of Churchill and Stalin.  Even though Henry Wallace, Roosevelt's moderate vice president during the war was replaced by the hawkish Truman in the 1944 Democratic Party Convention, even though Wallace was preferred by 62% of the delegates on the first vote.  But since a two thirds vote was required, the hawks engineered the election of Truman instead.  After that, the Cold War was inevitable and that resulted in the dysfunction of the Security Council. 

#6.   European Union 

The European Union is kind of a United States of Europe.  But the countries of Europe are multi-lingual with long independent traditions, compared to the colonies of America.  Both are good models for a World Federation that could be the next stage of evolution for the United Nations.  The European Union has entrance standards and direct election of the European Parliament.  Direct elections make the members of the Parliament authorities in their own right and tie the peoples of each country more directly into the European project.  Nationalism results from appointees as is the problem with the present United Nations.

Higher standards required to join the European Union stand in sharp contrast to the lower standards model of the World Trade Organization.  Requiring democracy and human rights such as health care and education as a condition of membership avoids the least common denominator problem in trade regimes.  Unlimited expansion of the European Union could eventually lead to a government of the world's democracies, with those left out needing to adapt democracy and social standards to avoid being left out of the world party.

#7.   World Trade Organization

The world trade organization is a form of world government of by and for the corporations and against the human amenities of the governments.  Unfortunately, this organization operates behind closed doors, secretly plotting against the rights of the world's peoples in the name of profit.  The key flaw is the lack of disclosure and accountability to the peoples of the world.  The ethos is that business organizations have superior rights to those of human beings and the democratically elected governments of human beings.  Exactly opposite to the European Union, the WTO lowers human rights standards while the EU raises them as entrance requirements.

#8    Regional Associations

The United Nations is flawed and incomplete.  Regions and continents of the world each have different needs, problems, and opportunities and all politics is local.  So it makes lots of sense to have countries in different regions of the world work out common policies and positions on various human issues.  Solving problems at the regional level, like South America, North America, Africa, Arab League, Far East, etc., allows for experimentation and a variety of approaches that can avoid leaving regional needs out of global agreements.

#9    Regional Federation

Regional associations can grow into Regional Federations like the European Union or the United States of America.

#10   World Federation

The biggest problem with a World Federation is the problem of a world dictatorship.  No one wants one person in charge of the whole world, with no where to run to or no where to hide.  Switzerland does not have a chief executive, it is run by a small council.  That is one approach to the world federation dilemma. 

Another approach is a two thirds majority vote requirement for world legislation three ways.  The United Nations could vote based on a nation's population in one vote, by a nation's economic size in another vote, and under the current structure of one nation one vote that protects the small nations from the large ones.  Thus world law would have to pass a stringent test of approval, a modified consensus if you will, that could be vetoed by either the developed nations, the populous nations, or the small nations.  Hence the United States and Europe could veto some proposals, while India and China can veto others.  And small nations can veto large nation domination in the current General Assembly.  Military matters would continue to be controlled by the Security Council.

In some ways the current system is unfolding along these lines, but piecemeal in one area at a time.  Trade is the first block of a new world order, while democracy and human rights are being left out because of the lack a broader general world organization.

Empire

If we do not find better ways to pursue world governance, we are doomed to wars and empires.  Here is the scenario of the stages of empire dominant civilizations go through:

https://www.academia.edu/5415354/STAGES_of_EMPIRE