Rome (or rather western rome, the east is... complicated) controls all of Italy, France and the west bank of the rhine, germania up to the elbe, Hispania, all of the british isles and north Africa (morroco to tunisia).
Rome is a republic again after a popular uprising in the 16th century, and is close to OTL liberal democracies. however, the empire is also a prosperous federation with regional capitals in Londinium, Paris, Carthage, Cologne and Toledo.
Religiously the empire is pagan, with the main ones including latin, celtic, germanic and north african beliefs. these are more umbrella terms than actual religions - pantheons and canons vary wildly across regions, and every small town has its own local god or saga that is known only there and in the great libraries of Rome. besides that, small pockets of jewish and zoroastrian immigrants live in the larger cities, and a tiny community of latin-chinese buddhists live in northern gaul - a result of the long-lasting roman occupation of southern and eastern china.
demographically, the empire is extremely diverse (no 80-95% ethnic latins here
) - celtic, germanic, north african and semitic peoples live alongside ethnic latins (mainly in italy, hispania and southern gaul and germania).
linguistically, bilingualism is the norm in the empire and multilingualism is as common as bilingualismis in OTL europe. besides knowing one of the staggering amount of languages and dialects in the empire, the vast majority is fluent in modern latin as it is the language of communication in the internet, across the empire and in its former colonies.
strength wise, the empire is the undisputed hegemon in the world.
besides having the second largest population in the world, the most overall and per capita GDP and the largest army in the world, rome is also absolutely dominant in africa, europe and america through the latin union - an economic and diplomatic union including rome and her latin-speaking colonies, meaning most of africa, the entire new world, europe, australia and the western indian states.
culturally, Rome has advanced much faster than OTL in terms of civil rights - the first wave of feminism ended in the 17th century with women being given the right to vote, and most sexual orientations were already widely accepted by that time. the only exception to this stellar record is slavery, which was abolished in the late 18th century after a brutal slave insurrection known as the fourth servile war.
Leftism also developed much quicker than OTL, with the equivalent of modern socialism appearing in the 15th century and gaining large traction in the 19th. fascism and right-wing authoritarianism is mainly shunned from the mainstream, as the fall of the empire (also popularly called 'the second kingdom') only strengthened the fear of Rome from all forms of dictatorships.