Yes it is another Brit-wank, its intentional and I am not apologising for it.
The POD is not exact but its somewhere in the Late 15th/Early 16th Century where the English discover the Americas and claim it for the Tudors. Like the Spanish of OTL they focus on the Central and Southern portions of the Americas and leave the “poorer” North to the other nations of Europe. The British Isles are united in a different manner and Britain goes from strength to strength, building an enormous empire.
Britain's closest rival is the Holy Roman Empire. Italy was united in the 17th Century and became a marginally powerful nation in the Mediterranean. In the late 18th Century an ATL Napoleon figure appeared and took over during an invasion attempt by the French and Spanish. This military genius lead Italy in a series of rapid military campaigns that lead to the domination of most of Europe. The military genius then declared himself Emperor of a new Holy Roman Empire. The HRE is still run by his descendants. The Emperor rules with absolute authority hidden behind an easily exploitable constitution and a number of administrative loopholes. The capital of Rome is enormous, home to 11 million and covered in shiny neo-classical architecture. The largest single building is the enormous and ornate Imperial Palace that dominates over 2 square miles of land not counting the gardens.
The Holy Roman Empire is authoritarian, repressive and militant. The Catholic Church gives support to the regime and preaches the superiority of the Emperor in their sermons. In return the HRE endorses the Catholic Church and persecutes other religions. Protestants, atheists and especially Muslims are actively discriminated against (Orthodox Christians are better off but not by much). The secret police are incredibly powerful and encourage the population to report any suspicious activities that their neighbours may be partaking in to the authorities. HRE authority is less obvious in their puppet states, especially the Protestant ones but they are all firmly under Rome's thumb.
Russia is a regional power and not really capable of projecting itself politically yet. Russia did move East earlier and did a better job of reaching more economically viable regions and did a good job of conquering Central Asia but they failed to make it big as a superpower. Russia went the populist route in the 1920s and is now an elected monarchy. The Russian parliament has actual power now and the Tsar's power is held in check by a constitution. Russia is a very codified and militant society. Social organization is very popular as are planned construction and business ventures. Russia is also very religiously tolerant though the Orthodox Church is still the most important and the only one endorsed by the government.
The British Empire is the world's largest superpower. The empire is now an immense, complex construct. Federalisation and the establishment of wings in government for rich/powerful locals has made the administration easier. Whilst the empire has moved on since their “police state” days, they are still very strict with their policies of modernisation. The empires strength is now in its colonies in New England since the rise of the HRE made living in Britain itself rather unpopular. Society is more reactionary and militarised as a result. The Empire still maintains its colonies in Asia and portions of Africa.
The colonies are now run with business-like efficiency. Local populations are about as enfranchised as anyone else is and the old ideals of scientific racism are now very old fashioned. Refugees from Europe have often been resettled in the colonies to help provide a base of white settlers for the colonies. Islam is very unpopular (due to the terrorist attacks) but is still legal to practice. The security state is still large but not as intrusive as the HRE's and most British citizens can be secure in their daily lives without being dragged off in black bags and black vans. British architecture is big on neo-Gothic styles to contrast and combat with the HRE's styles. The Empire is now firmly following the policies of equal rights for all races of the empire. Rich Asians and even a few Africans can be found in the formerly European and Creole upper classes. Big business is now very environmentally conscious and even women have been given the vote (voting requirements still exist and the government is too elitist for most to get properly involved but foreigners and women can get in).
Technology is at roughly 1970s level. The atom bomb was invented only a few years ago and nuclear power is very popular. MAD is a fairly new concept and being enthusiastically pursued by the world powers. The industrialisation of the colonial lands and the surprisingly fast rise of the Japanese economic superpower is beginning to worry people in high places. Computers are big clunky and excitingly new. So many possibilities are presented by these thinking machines and every nation is working to integrate them into the infrastructure of government, society and business.