An interview for the Today programme with Mark Mardell, the man who has my old job of BBC North America editor, has to be cancelled at the last minute. The reason: his house (late at night US time) and home studio have been plunged into darkness by power cuts caused by severe storms brought on by temperatures of around 100of. Ah, how this makes me nostalgic.

American weather is as bold and brassy and violent and revivifying as the nation itself. Washington was a hardship posting for British diplomats ‘til air conditioning was invented. It is sweltering with wet heat 24/7 in summer. I used to love it; loved the glamour of the discomfort, the sense that life was being lived in an alien place. Here we have piddling showers and watery sun. I fear my (almost) subliminal contempt for the British weather sometimes shows - on the programme later that morning I let an interview overrun and cut the time available for the weather forecaster. He is cross. "Sunshine and showers," I call after him as the studio door slams.

Actually I love being back. I thought I would hate it, but the job is fun and British politics is now almost as interesting as America's was during the Obama election campaign. Well, all right, not quite. I still hanker sometimes after the sheer fun of the American scene, and the story of Obama's decline, from walking on water to treading it, is fascinating. I have a framed note he wrote for my young children when I interviewed him a year ago - "dream big dreams", it implores them. When they look on it in their later years, or try to fl og it to help pay tuition fees, I wonder whether it will be seen as a message from the man who transformed America and the world, or a loser who followed Jimmy Carter into obscurity; an historical footnote (first black president) with no substance attached.

Many Americans have fallen out of love with Obama, but coming back here I am reminded of how important it is to millions of people that he succeeds. A friend asks me to go to a little theatre group near where I live in south London, where vulnerable and potentially troubled young people are being encouraged to use drama to communicate with each other and the world. I am there to advise them on journalism for a scene in their play, but we get talking about Obama and they plainly identify with him in a way they absolutely do not with any British political fi gure. They are a worldly bunch but stunned - mouths open - when I tell them I have met him. It's not hype: Obama's presence in the White House is an achievement of which millions of people are still quietly proud.

The Fourth of July, American Independence day, is celebrated with gusto in our home. My youngest daughter is a US citizen and told us recently that she is, in fact, only staying with us in London, not living here. She is six and is contemplating moving to Los Angeles, she says. She intends to go when she is, "like, seven or eight". Go for it girl: I love that American can-do attitude. Sadly all three children have lost their American accents and learned that "regular" does not mean "normal" in English-English.

The children's upbringing makes them rather expert when we go to Winfi eld House, the US ambassador's residence and the finest private garden in London outside Buck House, for the Fourth of July family picnic. They stuff their faces with popcorn but stand still for the anthem. Remember to do those two things and little can go wrong in America. It's odd seeing the neatness and politeness and slightly plastic friendliness of Americans up-close again. All they need is a picket fence and Winfield House could be in the American suburbs. It was even knocked down and rebuilt in neo-Georgian style by one previous owner: very Desperate Housewives and actually not much bigger than some of the homes American footballers live in outside Washington DC.

My son has Type 1 diabetes, an autoimmune disease whose causes are unknown and for which there is no cure. But I see that a firm in Sweden has made some progress towards finding a vaccine. They have sold the rights to market this putative medicine to the American company Johnson and Johnson. ‘Twas ever thus: America is not the home of invention but over the years since steam engines were attached to river boats, it has brought the fruits of human achievement to huge numbers of people. America is a relentless force for democratisation, sometimes insensitive but overall, I reckon, positive. If my son is cured one day it will be American vim and vigour (and desire to turn a buck) that delivers it.

Justin Webb is a presenter on the Today programme and former BBC North America editor

This article was first published in Total Politics magazine

Tags: Diary, Justin Webb