Hell, even if there were a public register of Trump asking them to remove an app, you could always argue, "Well, anyone, regardless of them being president of the United States or not, is free to ask for an app to be removed; anyone could theoretically demand and protest anything, and Trump, as any citizen, has this right" (not saying I agree with that thesis, to be clear).
But I do believe the whole point highlights a bigger problem: a negative relation between big corporations and the government. I'm not sure how anyone would solve it. Maybe by sidelining the whole issue by making it easier for people to install apps from whatever the fuck they want, without the app stores gatekeeping what software one installs on their device.
But if anything, we are moving far away from that, even on Android