I flew back to the US from London last week, and after waiting for two hours at immigration I stood by as the officer frowned at my documents. My children’s US passports had been scanned without a problem. But looking at my green card, the officer asked: “Was this lost or stolen in the last year?” As it happens, it was. “Then I’m sorry,” he said, glancing down at my three-year-olds. After a seven-hour flight and all that waiting in line, they were doing breaststroke across the JFK floor. “You’ll have to step this way.”

I have heard about the Congratulations, You Have Problems With Your Paperwork room at JFK, but until that moment had never actually seen it. It is a small, windowless room dominated by a raised bank of desks, behind which six or so officers sit, with several more patrolling the room. “No cellphones,” snapped a woman as I knelt on the floor, restraining a child with one hand while trying to text the cab driver waiting for us outside with the other.

“OK, I’m just – .” It took her two seconds to cross the floor and rip the mobile phone from my hand, an act so surprising I laughed. “Wow,” I said. “As if I couldn’t hate this frigging country any more.”

This was a childish thing to say. Most of the time I quite like the US. But more obviously, it was the purest expression I will probably ever make of the confidence that comes from being a white woman in possession of a British passport. “Now sit down,” yelled the woman. I stood up and looked around the room. The only empty seats were two rows at the back that had been pushed too close together to use. Alongside, a group of Hispanic men hovered uncertainly. Now we joined them. “Sit down!” yelled another officer. When nothing happened, he jutted his chin at the men, directing them to push apart the seats. “See what can be done when you work together?” he said sarcastically.

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This facetiousness seemed to me the most shocking aspect of the situation: engineering people into a position of powerlessness, then mocking them for failing to show enterprise. There was no time to dwell on it, however, because just then my phone went off. “Whoever’s phone this is, come turn it off!” bellowed the woman. As I approached her desk, she was momentarily distracted, and once again I started texting the driver. Her scream was so loud – “Are you TEXTING? And are you on MY SIDE OF THE DESK?” (I had inadvertently drifted) – I thought for a moment she would actually restrain me.

“Did you go the full Poppins?” a British friend asked me afterwards. But the fact is, I didn’t. I was suddenly frightened. There was no bathroom access in this room, and both my children were wailing they needed a wee. The officers were completely implacable. A Middle Eastern woman holding a tiny baby sent me sympathetic glances, and after an hour my paperwork was returned – no explanation, no apology – and we left. I am still furious and indignant about the authoritarianism of that room, but more than that, of course, at the awareness that we got off very lightly.

• Emma Brockes is a Guardian columnist