Pax Roman us is Roman Peace (Peace though military strength)

Pax Britannica would be the peace created by the military might of the British Empire.

Pax Britannica (Latin for "the British Peace", modelled after Pax Romana) was the period of relative peace in Europe (1815-1914) when the British Empire controlled most of the key maritime trade routes and enjoyed unchallenged sea power. It refers to a period of British imperialism after the 1815 Battle of Waterloo, which led to a period of overseas British expansionism.

Pax Americana , which means American Peace is a rather vague term but was used mostly after World War ended and the there were great hopes for a lasting peace brought about under US influence on the world. It is a modern reference to the Pax Romana and its successor the Pax Britannica. pax-americana

Pax Britannica (Latin for "the British Peace", modelled after Pax Romana) was the period of relative peace in Europe (1815-1914) when the British Empire controlled most of the key maritime trade routes and enjoyed unchallenged sea power. It refers to a period of British Imperialism after the 1815 Battle of Waterloo, which led to a period of overseas British expansionism.

The Pax Britannica lasted from the end of the Napoleonic Wars in 1815 until the outbreak of World War I in 1914, so it spanned approximately 99 years. It was a period of relative peace and stability enforced by British naval power and colonization, during which Britain dominated global trade and exerted significant influence on world affairs.