The Pope is well aware of the need for the Church to remain separate from partisan politics. In USA there would be huge tax implications if the Church were seen as supporting a political party or political candidate. This has caused some clergy to get reprimanded if they do so much as write something in the church bulletin about supporting one candidate or not supporting another, or attending a Trump rally in a Roman collar and getting shown on TV.
Also, voting in the USA is secret. Therefore, I doubt that the Pope would reveal how he voted, and might not even reveal if he voted. A normal, prudent Pope could send in an absentee ballot and not be seen going in and out of a polling place, and refuse to answer any questions asking “who are you voting for in the next election” etc.
As for the “Catholics will all vote for the Pope’s candidate or the Catholic candidate” worry, people already worried about that in USA when John F. Kennedy ran for office and actually had a chance of winning. (Previous Catholic presidential candidates tended to lose.) There was even a joke that the Third Secret of Fatima (which was supposed to be opened and read in 1960) said “Vote for John Kennedy”. The concern was that Kennedy would win and then the Pope would just tell him what to do, so Rome would be running the country. Didn’t happen.
I think the US is past the whole anti-Catholic worry about Catholics all voting a certain way because “the Pope says”. It was perhaps a bigger worry prior to Vatican II because Catholics were generally more obedient to Church authority then. Nowadays, heaven knows that post-Vatican II, American Catholics don’t hesitate to disagree with the Pope on everything and anything. So even if people knew how the Pope voted, 90 percent of them wouldn’t care.
