Once upon a time, the British monarchy exerted a unique hold over the imaginations of millions of Americans, an interest that elevated its crown-bearing figureheads above the average A-lister or Hollywood hoi polloi.

Lately, however, a succession of births, deaths and marriages in the royal family, and several high-profile scandals, have collided with the rise of an internet culture evermore obsessed with celebrity. The monthslong frenzy over the whereabouts of Catherine, Princess of Wales — culminating in a televised statement on Friday in which she revealed she was battling cancer — reflects a fundamental shift in the sentiment of a growing faction of the public: that the Windsors are like any other celebrity family in the public eye, and that they deserve to be treated as such.

The online maelstrom that fueled KateGate came largely from outside Britain — and especially from across the Atlantic. It exploded thanks to a 24-hour news cycle, a boom in conspiracy theories and rabid social media punditry, as millions of users sought clicks and a boost in followers with increasingly provocative posts.

“Everyone is watching a different thread on their phone, following a different theory or even becoming an armchair expert or sleuth broadcasting about the royals from their living room,” Wendy Naugle, the editor in chief of People magazine, said last week.

These days, many of Ms. Naugle’s American readers follow every update about the British royals as they would other celebrities — “for the outfits and family drama,” she said. And while millions of people wanted only to offer well wishes to the princess, the criticism, mockery and expectation that interested parties should be given boundless information about her reached levels rarely seen before.