I spend about two to three months a year in the UK and about six in the USA. Britain's decline started well before 2008. It started to be very noticeable in the late 90's. The financial crisis, COVID-19, and many other factors only worsened it but the rot was already there.

If you want to blame the USA, you need to go back further to them insisting on the UK paying back the Lend-Lease act in full while they poured money into Germany and Japan to rebuild. The UK has the worst infrastructure in Europe where I spend my other 90 days. :)