He was. With the exception of George W. Bush, the DC Universe has all the same US presidents that we’ve had in our own United States. Trump could be heard “off-panel” sporadically through the 2016 Suicide Squad series, being manipulated by Amanda Waller into patronizing her Task Force X until he pulled the trigger on an even foolhardier super soldier program he called “The Wall.”
He later plays a small but significant role in Doomsday Clock, publicly turning the government’s back on Superman and other metahumans as a means of burying the US’s illicit involvement in the Firestorm project and other metahuman experiments – ironically, a move intended to keep himself out of jail. Despite this, when Black Adam and his Kahndaqi metahuman criminal refugees arrive on the White House lawn to take the president into their own custody, Superman returns to stop them. Through all this, Trump is never named, nor is his face shown on panel, but the implication through his action, speech, and mannerisms are all indicative of author Geoff Johns’ intent.
The popular story is that it was Power Girl co-creator and famous comic pin-up artist Wally Wood who did this through her initial appearances in All-Star Comics #58-65. But when you look into the actual drawing, no such mythical cup expansion is visually present.
So, how did this myth come about? Who’s responsible for this misinformation? Probably, Wally Wood himself. A bit of a sensationalist with a bawdy sense of humor, Wally allegedly liked to tell people when the subject of Power Girl came up that his intent was to draw her with a larger chest in each issue until somebody called him out. This was likely meant as a joke, and not something he ever actually went through with. But somewhere along the telephone line, and because people aren’t too careful about checking their sources, what started as an artist’s flight of fancy became popularly accepted as something that actually happened.