As one who grew up in America, I am most at ease with the 12 hour clock.
However, when I am talking to my friend in the UK, I convert to 24 hour for him. The more I do it, the more sense it makes to me. It eliminates potential errors in speaking and writing the time;i.e. screwing up AM and PM. The US military uses it, and like the phonetic alphabet, reduces potential confusion and errors.
If one wanted to stretch the point a bit, one might say continued use of the 12 hour clock, and the avoidance of the metric system, represents America's ethnocentricity and it's insistence that everything we do is right, and screw the rest of the world. All science, in the US and the rest of the world, employs metric measurement, and most of the world uses the 24 hour clock.
And finally, it eliminates one of my (silly and pedantic) pet peeves - people saying "5:00AM in the morning". Well, it can't be 5:00AM in the afternoon, can it? Another dopey redundancy.
(Yes, I know I'm a fussy jerk. 😱)