[gargan]

The UK and US are both equally nations of immigrants in 2025 at about 16% of the population being born abroad. The UK constitution is written but uncodified and unites the country under the King. The constitution can slowly change to deal with immigration, but in the US they're stuck with either what you have or violent revolution...

[Saline9515]

I was referring to when the political systems were set in place. When the UK became a parliamentary monarchy, no one could dream of becoming "a nation of immigrants," while in the case of the US, it was obvious that it was and would be for the next century, at least.

The US political regime was designed for stability by lawyers, which has worked quite well for the country so far. In the case of the UK, the lack of a constitution can also be quite dangerous as it allows abuse and doesn't guarantee any protection of basic rights or even democracy. This can work well if the country is mono-ethnic, with elites and plebeians sharing a common culture. It can also easily derail in pluri-cultural settings where ethnicities compete against each other to impose their standards or acquire resources from the state. This is what happens in Africa, for instance, and one of the reasons for the weakness of the state there.