Right now, you’re able to select the appropriate gender marker on your passport without a note from a medical professional (and a passport can be used in the vast majority of situations you’d use a birth certificate) but because the self select gender marker was done by executive action, it’s extremely likely to be reversed when Trump takes office.
Also, having one might be a good idea in general.
This sounds like exactly the type of thing they’ll reverse, either through executive action or pushing through the GOP Congress and Supreme Court. If you can afford it, go for the full US passport.
What incentive would they have to tamper with passport cards? They’re pretty popular in the border regions as an inexpensive way to get an international travel document.
They are also mentioned in several international treaties, particularly with Canada and Mexico. The president doesn’t have the power to unilaterally abrogate those treaties.
Honestly, I doubt they’d mess with the cards. They’re extremely common and useful for people who live in border states - Minnesota encourages them at our DMVs, and if you know about the northwest angle it’s likely a big part of why.