Unabashedly romantic and optimistic, the sumptuously filmed “Red, White & Royal Blue” is an easy-on-the-eyes fairy tale in which the ridiculously handsome son of an American president engages in a secret relationship with an impossibly gorgeous British prince. It’s a royally implausible affair, but also a fun piece of fluff that never ceases to entertain.

A romantic comedy needs a meet cute — or in this case, a “meet cake” — and “Royal Blue” serves up a doozy when Alex Claremont-Diaz (Taylor Zakhar Perez), the first son of the United States, skirmishes with nemesis Prince Henry (Nicholas Galitzine), resulting in a disastrous dessert mess at a royal wedding.

Naturally, or not, this frosting-laden fiasco creates an international incident in which the powers-that-be on both sides of the pond force the two men into a kiss-and-make-up PR campaign. But no one — particularly Alex and Henry — has any idea just how much kissing and making up is about to happen.

Director-writer Matthew Lopez, the playwright behind the epic Tony Award-winning “The Inheritance,” revels in showing off a lighter touch here. But he still operates on a large canvas: The film deftly moves back and forth from the White House to palatial English estates, giving the movie a big-budget feel. Rarely does a frothy, LGBTQ-themed romantic comedy feature film get such treatment.

The idealistic Alex and the droll Henry have a natural chemistry, whether it’s lobbing funny one-liners or pawing each other in the closet or bedroom or wherever they can find a place away from the glaring eye of the public. (The level of sexual antics doesn’t rise to an R rating, but the MPAA thought differently.)

Lopez helps out his young leads by surrounding them with excellent actors, most notably Uma Thurman as the president, Stephen Fry as the king and Sarah Shahi as a campaign operative. They all inhabit a lovely fantasy world in which discrimination seems virtually nonexistent and ruby red states can magically turn blue.

Not much of what occurs in “Red, White & Royal Blue” is grounded in reality, except for one crucial element: the characters. And that’s what ultimately makes this love-conquers-all film a pleasure to watch. We believe in the romance and the emotional journeys of the two lead actors, hoping these men will overcome the long-held traditional barriers standing in their way.

When their relationship reaches a low point and Alex flies across the Atlantic to confront Henry about his disappearing act — in the middle of the night, in the pouring rain, at a remote country estate — it’s deliciously preposterous. But we quickly forget about the silly setup, because the longing between these men is so genuine and heartfelt. It doesn’t matter that this is a prince and a president’s son: These are two humans trying to find each other, and at the end of the day, that’s what this movie is about.

洛佩兹选择一个克制的结局——至少排版ared to what has preceded it — a wise move that only adds to his film’s crowd-pleasing aura. Though the fluff factor is off the charts, this is a project the director and his cast clearly believed in. It’s not easy to make an amusing, accessible diversion that mixes LGBTQ positivity and national politics, but “Red, White & Blue” passes the test with flying colors.

David Lewis is a freelance writer.