The main reason to publicize it all is to pressure other governments to also donate more. It's not like keeping it a secret would have a huge impact on the battlefield either, they'd find out soon enough the hard way, if not through intelligence gathering. (which they admittedly seem very poor at)
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Partly that. It's also to help maintain a measured ladder of escalation. Russia crosses a line, the US responds, and then the next escalation is a separate decision. If Russia thinks it is crossing lines without a response, that would be bad and might lead to further escalation. If Russia thinks that the US is responding arbitrarily, that would also be bad and could lead to further escalation. Yeah, it sucks that the US always has to be the responsible one, but these days Russia's shtick seems to be that they don't care if the whole world burns if they don't get their way.
Cluster Bombs weren't given to improve Ukraine's standing per se, they were given because we ran out of M795 standard issue shells.. Then, we bought South Korean shells to make up the difference. Then we ran out of those and are now forced to give them cluster munitions (which we have a large stockpile of but never intended to use).
We still don't like using them, because each cluster-artillery shell scatters 4 to 5 grenades into Ukrainian soil that may kill a farmer 50 years from now. So even as we give them to the Ukrainians, we tell them to use them sparingly and only when absolutely necessary, as it will damage their own country every time they shoot that shell.
We didn't really give Russians warning with regards to Phoenix Ghost drones, I don't think we gave them warning on Excalibur precision (1m accurate) 155mm shells, I don't think we gave warning on many other munitions. Etc. etc.
Plus we're clearly undershooting our estimates and giving much more. Russians will try to estimate how many international gifts they deny their enemy, counting ammo cases around arty dumps before dropping incindiaries, etc. It makes sense to give Ukraine ~20% more than we advertize, so that if/when Ivan says "we got all the advertized Himars or Drones or whatever" they can get a nasty kick in the balls for taking the risk to escalate, believing the threat is gone.