Credibility didn’t seem to matter too much when a game show host pushed through $2 trillion worth of permanent tax cuts through in the US five years ago!
Anyway, the US may be in “a bit” of trouble but it’s clearly nothing compared to us. Successive US governments have been able to push (broadly) inflationary fiscal policies and get away with it for three main reasons. One - a global reserve currency that will always find buyers, no matter the macroeconomic pressure…..which we don’t have. Two - a competitive market of 300 million consumers on its doorstep, which is very useful to have when your economic policies are solely focused on unleashing growth. We also don’t have this - or at least, we voted to leave the closest thing we had to something similar in 2016.
Third is the luxury of ultra-loose monetary policy, where a credible, independent and powerful central bank has enough ceiling space to chill the economy if pro-growth policies lead to prices running too hot. The US had the foresight/luck to get their policies out the door before monetary policy really began to tighten and as you say, even still may not fully get away with it. Truss inexplicably decided to try a similar act even though she knew the window was closing, if not already shut. Presumably she either thought the power of the UK economy, or the power of the Bank of England (who have not covered themselves in glory) would be enough to see us smash through regardless. Unfortunately we’re no longer the economic force she thinks we are, and you need to do more than take the chains off to win a weightlifting competition.
The whole thing is a humiliating lesson in British hubris and the folly of our economic exceptionalism. We’ve tried to dress up as Uncle Sam and came out looking like Greece. To try and compare us favourably to Italy - a country with no ability to tweak its own monetary policy, and one that goes through Prime Ministers faster than the Tory party goes through chancellors - shows us precisely how bad things are right now. We should be running rings around Italy right now - at least, wasn’t that the point of 2016?