According to a Redfield & Wilton Strategies poll released Monday, Britain's new prime minister has a net approval rating of negative 61 percent, down 13 percentage points from a similar poll last Thursday. Only 9 percent of respondents approve of her overall performance, while 70 percent disapprove.Definitely not a Republican president. I think Bush hit 24% once in a slight outlier poll, but basically "27% is the hard minimum, certainly for Republican presidents" is likely true.
There isn't one explanation for the difference between the countries, though the many partial explanations are interesting!
And it isn't as if the UK has (metaphorically) blown up yet. Worrying things, but nothing that catastrophic has actually happened.