Analogously, divisions between Myanmar and its bordering nations prior to WWII were unimportant. The British East India Company slowly expanded to the whole of Burma. By 1886, Burma was annexed to India, then became a separate colony in 1937, but important borders were never established. For example, people of the Karen ethnicity who live on what is now the Thai-Myanmar border, the Meoi River, historically operated on both banks of the river. However, after WWII the Meoi River seemed like a good arbitrary border between the two new nations and thus the Karen people were divided into two countries.
Dozens of ethnicities with over a hundred different languages and three hundred different dialects were thrown together along unrealistic boundaries into a new nation. Without any sense of unity, it has been exceedingly easy for the Myanmar junta, powered by the ethnic majority Burmans, to "divide and conquer" the various factions and thus rule them with little to no rights
while funding their regime with the land's plentiful natural resources. Oil and natural gas are piped from Myanmar's coast directly to India and China. When the junta (called the SPDC), is in need of funds, they auction off millions of dollars of gems, mostly to China.
While the UN and the US have economically sanctioned Myanmar, China and India, the two most populated countries, continue to trade, taking advantage of cheap resources to fuel their own economies. This is also strategic, as if one or the other super-powers were to cease relations with Myanmar, the other with indubitably exert tremendous influence on the only nation separating the two. As a result, the junta is propagated and becoming richer. With the millions of dollars of oil revenue, they purchase MiG fighter jets, more guns, and train more troops while the majority of the population of 58 million lives without education, health care, or even roads.
To say its "all England's fault" is hardly fair; the Myanmar situation seems almost inevitable after the solid nation-state borders of India, China, and Thailand boxed such a diverse loose collection of people together who previously never had outside authority exerted upon their small tribal cultures.

Myanmar, for me, is a case of too much diversity in a world where diversity is considered a golden truth to be put in a special box and saved forever. Like it or not, Myanmar people are stuck together inside their country and need to find unity amongst themselves before they can hope to influence the junta controlling them.