Here's a small fix. No attention was paid to formatting and semantics, i'll halp with that when you ahve the final version roleld out =)

I avoided rephrasing entire sentences where I could as not to change what you meant, but there were sections that simply did not make any sense whatsoever, so I tried to guess what you meant by them and put it into words xD. In general, don't be afraid of the period. It makes it much easier to read if you have more smaller sentences, rather than oen that spans a line and a half. Especially when it covers multitude of topics - See 1st sentence of the race description. You used one to describe height, life expectancy, what food do they eat, and at the end - oh yeah, they are mostly human. I would start with saying they are msotly human, and then follow up with the differences, just one or two at a time.

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Name of nation: United Nations of Rathlar
Species:
[hider=Harthal]
The average height is 1.73 meters, the life expectancy is over 80 years, some live to 120. They are omnivores, in everything else they are almost human, except for one thing: all of them have a mark in the right hand which symbolizes Rathlar, the planet on which they live.
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Description of government: United Nations
-They are an entity on the planet which tries to bring balance to the world and unity is conformed by various member states which can vote in the Great assembly on various things (example: Program to bring help to some part of the Planet etc.) The Greatest position is the "Representative Of Rathlar", which is selected between all nations. Anyone in the world can postulate but the different spheres in the world support the candidate which aligns with their ideology or agenda.
Planet: Rathlar. This planet is the biggest habitable planet in the Milky Way, almost about ten times as big as Earth. About 2/4 of the surface is covered by an ocean.
Description of military:
[hider=UNR]
-The UNR uses military only to defend the peace in the world, but their military is limited by the support of other member states and great powers. Because of this they have one of the more advanced forces of the world, but medium in size.
-In Rathlar, the doctrine of Combined Arms has advanced more than others doctrines and the UNR uses this doctrine too: Aircraft, Ground Units and Naval Units have similar development and one cannot advance without the other. The Great Powers in Rathlar plan to use this doctrine in space too, making a mix of everything.
-The Airforce is based on attacking almost everything present in the battlefield. Because of this they have a great payload, from anti-naval missiles to air-to-air missiles. The UNR have designed the most advanced aircraft in the world, with help of other nations of course. This is the RN-105. Only the UNR have the facilities to make it and currently is denying any petition for this airplane. The rest are common 5th generation Harthal Airplanes.
[hider=RN-105]
[img]http://i60.tinypic.com/24y9rh1.jpg[/img]
This Aircraft is the first orbital fighter and bomber in the world. Actually, all the nations which helped in the development have the airplane blueprints (All nations). It has been designed to get very fast to any point on the world and can be converted to bomber or fighter depending on the situation. The RN-105 can get to the Orbit of the Rathlar and some of it weapons can engage in an orbital bombardment.
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-The Ground units are 5th generation too, except for one: the RT-520 tank. This was exclusive for the UNR and no one else has access to it. It currently is the best tank in the world, but the UNR can only produce it in limited amounts.
[hider=RT-520]
[img]http://news.hisstank.com/wp-content/uploads/sites/8/2013/08/Massive-Black-GI-Joe-Tank_1338577914_1377956603.jpg[/img]
-Naval Units are 5th generation, nothing special here.
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[b]Technological Overview:[/b]They are as advanced as late XXI century Humans. They currently have more industrial techs than spacial ones, the only two techs ahead of their time are the nuclear fusion and Super High Speed Internet and radio transmission. Nuclear fusion is revolutionizing the world, albeit with it's own problems - the 2 greatest spheres of influence in the world are currently developing a weapon of mass destruction based of Fusion, Which is making the world go to the abyss. Super High Speed Internet and radio transmissions is a technology capable of sending transmission faster then light itself, but only with a great antenna with high power supply. The Tech was made to make the communication easier since the planet is 10x Earth's size.
[b]Cultural Overview:[/b] There are two large fractions, one thinks that the democracy is good and the other side thinks that the monarchy is good. Both sides share a global culture thanks to the UNR, but that is only thing they have in common. Both sides have their own costumes and religions (maybe 2 Jesus). The democratic side has more liberal and socialist ideology and the Monarchy side has Fascist with communist ideology.

[b]History:[/b] Rathlar History started to be written 5500 years ago, in different places almost at the same time. The war and civilization started to flourish about 4200 years ago. At that time the total population was 500 million people. Different civilizations and cultures started to expand as the commerce and discoveries advanced. In the year 600 BC(Before Contact) there were about 30 predominant empires around the planet, all making alliances with each other and fighting between them.

There are two continents important to the history, Astalth and Zurtk. Both of them have great civilizations, great armies, great culture and great expasions. They were separated until 1400 AC (Age of Contact). Zurtk developed the goverment of Monarchy, comprising of stable states all controlled by a monarch. Astalth had only known Democracy, making them semi-communist and liberals. When both forms of government were in what we call the Dark Ages, they meet each other. The result was disastruous. When the delegations of both continents met each other, they could find only differences and hate. Since then there was always a battle for power. When the age of colonization started, nations from both sides fought for land until the end to get what they wanted. They couldn't accept a peace treaty, like in our timeline. The only major event which disrupts our time line is the Great War - the only great war in Rathlar, Year 1940. A crisis centered around territorial claims for a big island in between of the two continents was fatal. The distance which stopped any kind of war at major scale between both continents was overcome, the new inventions like the airplanes making it easier to fight over distance. The Island called "Rathlar Abyss" was never disputed between any nation until present day. On both continents the most powerful state claimed the island for themselves. There wasn't any long talk about this, there was only one order to give, "Fire". The moment which both continents were waiting for centuries was going to start. Before the war the world had 30 Billions of Harthals alive and at the end there were only 19 Billion. Landings, naval combat, ground battles and Air fights were waged for about 20 years. Both continents drafted all the population they could, in total 10 billions men were drafted. It was all crazy. In the most radical nations of both sides it was decided to educate children in combat since 6 year old and others drafted them from 12 years old. In middle of the chaos, the nuclear power was discovered and with the final weapon at hand for both sides. This world would have been only ash by now if it weren't for this weapon. It was the end of the Great War. Both sides knew what was coming for them if they sent the order to launch a nuclear bomb. A truce was made, for this the UNR was founded - an organization to search the peace of the World and to maintain the truce forever. Since then both sides entered the cold war , both sides supporting the UNR trying to get all the influence they can.
Other:  
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As mentioned above, communism and fascism don't mix too well, in fact they were each other's worst enemy. If the planet is 10 times the size of earth, it either needs to be hollow or the people insanely strong to withstand such gravity. Also, you mention the two continents meeting in a "dark age" - that doesn't look like good age for intercontinental sailing to be achieved :D