In 1870, Britain was the top producer in both coal and steel, by 1900, Britain was tied with America in coal and imported most of her steel from the states as well. Meanwhile, America enforced harsh tariffs on British goods to grow her own industrial economy, which worked wonders. Other questionable policies like allowing migration to America instead of directing them to the dominions resulted in the empire losing 15 million people to the US by 1920, if you count their descendants. Protectionism against American goods would have resulted in Britain keeping her industrial edge for a few decades longer at least, and with the Irish and other British emigrating to the commonwealth, the Empire very well could have entered the 1920s with a White population north of 70 million instead of the 55 it was IRL, which would be enough to remain competitive with the US for a few decades more instead of becoming a junior partner after WW1, and a vassal state after WW2.
Instead, the financial class made a killing importing cheaper goods to the detriment of Britain's position as the world power, and ultimately doomed the empire while they all scampered off to New York. A story which should sound eerily familiar to Americans today.