When the Earths converged into one after the Second Crisis, it conveniently didn't collapse upon itself. However, the size of the Earth in DCURPG is somewhat different from the one in the 'Real World', considerably larger, having several more countries and locations worth knowing about.

American Locations

The main setting of the roleplay, the United States of America has a few places not everyone, even in-universe thanks to the Convergence, are aware of.

Xavier Institute: With two campuses, The Xavier Institute for Higher Learning located at Greymalkin Lane in Westchester, and the Massachusetts Academy, located in Massachusetts.
Xavier Institute for Higher Learning: When Emma Frost finally awoke from her coma, she and Banshee decided to convert her Massachusetts Academy into a new "School for Gifted Youngsters" and train Generation X. Professor X agreed to pass on the title while his ancestral home was renamed the Xavier Institute for Higher Learning. While the Massachusetts Academy operated as a training facility for younger mutants, the Institute acted as the headquarters of the X-Men.
Under the influence of Cassandra Nova, Professor Xavier publicly outed himself as a mutant. After this revelation, the Xavier Institute once again opened its doors to students, this time with a greatly increased enrollment. To house the new students, an X-shaped dormitory was built behind the mansion. Because Cerebro gained a nanotech body and was eventually destroyed, Professor X and Beast created Cerebra to serve as their new mutant tracking, telepathic computer. The school continued to face challenges from outside, such as protesters and the fanatic cult, the U-Men, but they also faced challenges from within, such as a possessed Professor X, a student-led riot, and Xorn forming a new Brotherhood of students and destroying the mansion. Prior to its destruction, Professor X decided that at the end of the term he would step down as Headmaster and pass the reins onto Jean Grey. Unfortunately, Jean died in the confrontation with Xorn.
Massachusets Academy: The Massachusetts Academy was a college preparatory school for grades seven through twelve, founded in the 1700 in the Berkshire Mountains of Snow Valley, Massachusetts. The Academy was one of the oldest and most respected college preparatory schools in the United States. Run by a board of trustees, a young mutant Emma Frost became chairperson of the board and ran the school.
In addition to a large student body, Frost recruited young superhuman mutants and trained them in the use of their powers at her school, so that they might use those powers on the Inner Circle's behalf. Most of these mutant students were members of a team called the Hellions.

Utopia: Utopia was the main headquarters of the majority of the mutant population and the X-Men. Utopia first began as Asteroid M, the orbital space station of mutant terrorist Magneto. Asteroid M had several levels, including an observation deck, hangar bays, medical facilities, technology that kept it concealed from standard detection technology, and was positioned in stationary orbit, probably over Anya Lehnsherr's (Magneto's eldest child) grave. Magneto completed construction on Asteroid M just before recruiting his original group of Brotherhood of Evil Mutants. It was destroyed in a battle with the original X-Men, when someone was suspected of hitting the wrong buttons that would initiate the self-destruction of the base.
Many years later, Utopia was brought back to the surface by the X-Club, under the direction of Cyclops. Seeing no other option, Cable decided to move the mutant population (then stationed in the Marin Headlands at Graymalkin Industries) to this island, and off U.S. soil to avoid further persecution by the government, and G. Gordon and his H.A.M.M.E.R. in particular.

New York Locations:
Triskelion: The Triskelion is located between Manhattan and Brooklyn in the Upper New York Bay on Governors Island at the mouth of the East River. Each of the three wings that radiate from the central hub serve a different purpose. One wing is the headquarters of the Elite Squad, a team dedicated to solving problems of all scopes before they become an issue for Earth and the entire Prime Universe.

Arcane Asylum:

European Countries

Something something Europe.

Latveria: Latveria, officially Kingdom of Latveria is a small eastern European country within Europe. Its capital and largest city is Doomstadt. It was ruled by Dr. Victor von Doom aka Doctor Doom. It shares with Symkaria the border of Lichtenbad. Colossus also hinted Transylvania was located to the west of the Latveria-Symkaria region. It formerly bordered Rotruvia, which Doom annexed at the early times of his rule. Surrounded by the Carpathians to the north and the Malhela range to the south, Latveria has remained protected from the strife of neighboring countries.

Symkaria: Symkaria, officially Symkrija Kiralysog (the Kingdom of Symkaria), is a small eastern European country within the Balkans. It had been conquered many times over the centuries. It has maintained close ties to the nation of Latveria. Its capital and largest city is Aniana. At some point, Symkaria fell into chaos, due to a very violent revolution. When Symkaria fell, the Symkarian Embassy in New York City closed, and Silver Sable bought the building anonymously to use it incognito, intending to give it back once her country would be restored.

Markovia: Its monarchy was established around 1776. During World War II, Markovia was occupied by Nazis. When they were defeated, most of the Nazis were banished from the place by the United States Army and the kingdom was restored under King Victor's rule. However, Baron Bedlam, a former Nazi who had occupied Markovia, tried to reclaim the throne several years later, causing the death of Viktor. In the ensuing armed confrontation, Bedlam tried to murder the rightful heir Gregor, but he was stopped and defeated by the youngest son of Viktor, Brion, who had gained super-powers and become Geo-Force. With Bedlam out of action, his army was easily defeated by the Outsiders and peace was restored to Markovia.
Shortly after the ascension of King Gregor, Markovia had its first elections for prime minister. The race was between the bureaucrat Wilhelm Vittings and academic Josef Müller. The country was new to this circus, and violent arguments filled the streets. Vittings was in league with Baron Bedlam (or actually, Psycho-Pirate in disguise), and he won by default after Psycho-Pirate mind controlled Müller to commit suicide.