Post 6 and above,
Thanks for the info. Prior to you, I wasn't actually aware of any organization which actually prescribed or issued any XD series firearm. Apparently, Michigan has a few departments, which I'll make a mental note for my own knowledge.
I was mainly issued Glock through my career.
Calif. Highway Patrol I hear issues an S&W M&P model (.40 I think);
Nevada Highway patrol is issuing some model of SIG P320.
Local agencies I've mainly seen Glock, but some allow personally-owned pistols of various makes, models, and calibers which can become almost impossible to keep track of in my mind, if I can even find out what.
Of course, as most have heard, FBI has been issuing Glocks, but probably still allows some variety of personally-owned handguns.
Customs & Border Protection went with GlockT (with three models being decided upon by its management for issuance, not particularly an individual's choice of which model).
The military, which might include its police functions, too, are SIG M17 or M18, but depending on exact job or designation, probably deviate (whether SEAL, NCIS, OSI, etc.)
USCoastGuard went with Glock. I don't know how large number-wise they are and don't quite understand whether the OP (or I, for that matter) considers them "police" or something else.
Until with Post 6, and the XD, I'm also unaware of any departments using HK or Walther, but I suspect somebody out there will know of at least one in all the USA.
In the mid-2010s, I was also told by a Glock representative of the 65% to 80% estimates for Glock & LE, but this was before the LE adopting the, then, newly designed SIG P320 models, which I can only suspect has eroded some of the Glock LE usage percentages.