3:2 prints on A2 with a 36mm white margin all around.
16x24 on 17x25 looks pretty crappy unless you're going to mount/mat/frame it, in my experience.
That's a matter of personal taste and preference. It also depends considerably on the particular image and how the image is framed or otherwise presented for viewing.
Since I'm in the US I have to print to US standards. What would your recommendation be for a print in US sizing in the same approximate size range as A2?
There is no one right answer, and 17x22 inches, A2, and 17x25 inches are all reasonably-available photo paper sizes in the U.S. If you want to print a full 3:2 image
and maintain even margins on all sides--and that's again a personal preference and aesthetic choice, not a law of physics--then these are your options:
(1) 17x22 inch paper containing 10x15 inch image and 3.5 inch margins on each side,
(2) A2 paper containing 13.7x20.6 inch image and 1.4 inch margins on each side, or
(3) 17x25 inch paper containing 16x24 inch image and 0.5 inch margins on each side.
You can actually calculate this easily for any paper size:
single-side margin = image aspect ratio * paper short side - paper long side (where aspect ratio is ratio of long side to short side)
And of course, with an appropriate-size trimmer, it is easy to trim any image size on any paper size to even margins. Rotatrim, Dahle, and others offer a variety of models.