It was a shock, recently, to realise I can apply to become a US citizen next year – the statutory five years after getting my green card – and, to my much greater surprise, I discovered I actually want to. I’ve never wanted or needed an American passport. Besides which, I’ve always been vaguely neurotic about the downsides to dual citizenship: primarily, the question of what happens when you get kidnapped in a third country and neither of the countries to which you hold citizenship regards you as squarely their responsibility. (I realise this takes a rather rosy view of the Foreign Office or the State Department leaping to one’s rescue in any circumstances. But still.)

Plus, of course, it is a very odd time to want to become an American. It’s just a question of bureaucracy, I told myself; a green card is inadequate protection in these anti-immigrant times, and the idea of my children having inalienable residency rights where I don’t is chilling. Handy things come with citizenship, too, of course: voting, the opportunity to get arrested without being deported, smoother passage through JFK. And it would be madness not to do it, when the cost is filling in a few forms.

All of these things made sense to me intellectually, but failed to explain a weird fact: that the moment the prospect of getting a blue passport arose, I found myself completely thrilled by it. Not just thrilled but inclined, suddenly, to look at America differently. I have lived in the US for 10 years, and not only never considered it home, but tended most of the time to disparage it.

And I don’t mean the kind of affectionate disparagement most British people here reserve for home. Brits I know in New York tend to talk about the UK as a silly little country, with its underpowered prime minister and Brain of Britain Jeremy Corbyn, while being fairly certain of its basic superiority. I criticised the US not in this way – lightly, from a distance, with an underlying love – but instead often with vehement dislike: the grindingly hard economics of the place, the fact that all people do here – and for good reason – is talk, think and worry about money; the lack of social care; and that’s before you even get to the White House.

It’s corrosive to live in a country one purports to dislike, particularly when one’s children sound like Americans. (Well, almost. They’re clinging to the correct pronunciation of “bath” at the moment, although I have lost the battle on “water” and “can’t”.) And yet the second the chance to get a passport came up, I found myself not only grateful to the place but, for the first time, invested in it. You can give up your green card and go home, but citizenship, even after moving, feels irrevocable.

I should have known it wasn’t merely a question of paperwork. Years ago, a member of the South African consulate in London suggested I apply for a South African passport – my mother was South African before naturalizing as British – prior to moving to Johannesburg for six months and I found myself recoiling. Yuck, I thought; I did not want to be a white holder of a South African passport, even in this day and age.

These things are emotional, and they creep up unawares. At a beach on Long Island this weekend, I noted the huge American flag affixed to a neighbouring beach hut and felt a familiar surge of scorn, before finding it checked by some other impulse. Not national pride, obviously (I haven’t completely lost my mind), but the small, satisfying sense of being implicated.

•Emma Brockes is a Guardian columnist