So "Racist History" has a video titled "Racist History of Chinese Restaurant" where they claim that the US has a lot of Chinese restaurants because of historically racist immigration laws with a loophole for restaurants.
It is amusing how Americans love to explain various phenomena as uniquely American, when in a global context they aren't so special (this being a form of US exceptionalism). And how liberal Americans blame racism for everything.
Having been to more than 30 countries I have seen Chinese restaurants are everywhere, even in countries with a lower Chinese population than the US. Chinese people set up restaurants all around the world.
I don't know what the video's source of there being 45,000 Chinese restaurants in the US today, but let's take it at face value; Chinese Restaurant news, the "largest monthly publication that specialized to serve American-Chinese restaurants in North America", says that "There are more than 36,598 Chinese restaurants in the U.S".
The number of Chinese restaurants in the UK was estimated at 7,000 in 1984 (China to Chinatown, Chinese Food in the West, Roberts, 2002, quoted in Consumer Culture and Chinese Food in Britain, Featherstone and Tamari, 2006).
The US population in 2017 is estimated at 325.7 million and the UK population in 1984 at 56.42 million - just under 1/6 of the US. So once you correct for total population, there is a very small gap in the number of Chinese restaurants in the two countries (for completeness, if the UK population in 1984 had been the same as the US's in 2017, a simple extrapolation means it would've had about 40,400 Chinese restaurants - 90% of the US figure given by the video).
The UK does not seem to have specifically targeted Chinese or yellow immigrants as the US did. There was the 1919 Aliens Restriction Act, but unlike the US's Chinese Exclusion Act it didn't target the Chinese. Nor did it ban immigration. And neither the original Aliens Restriction Act 1914 nor the Aliens Restriction (Amendment) Act 1919 placed extensive restrictions on immigrant employment (only on Civil Service jobs - note that the restaurant loophole is the central claim of the original video). To say nothing of how many ethnic Chinese came in to the UK via the colonies (before the Commonwealth Immigrants Act 1962 many of them could go over).
Consider too that the ONS's, "Focus on Ethnicity and Religion (October) 2006" is cited as giving a figure of "over 400,000" for British population of Chinese descent. In 2006 the UK had 60.6 million people in total. So about 0.7% of the UK is of Chinese origin.
Compare that to 1.2% being ethnically Chinese in the US according to the 2010 US census. So relative to the UK the US's slightly greater number of Chinese restaurants is more likely to be explained by a greater number of ethnic Chinese than a restaurant exemption in migration rules (Keith Productions notes that in the UK in the 1960s, "Electric washing machines lead to a decline of Chinese laundries and many Chinese mom-n-pop operations switch to the thriving Chinese-restaurant business", which suggests another reason for the number of Chinese restaurants; incidentally it also says that in 2001 there were 12,000 Chinese takeaways and 3,000 Chinese restaurants in the UK, which means the UK proportionately has a lot more Chinese places than the US).
Evidently, this video's claims are suspect.