An example is the law against distributing information on making bombs/weapons with the intent of promoting/enabling violence.
US Code, Title 18, §842(p)(2)
(A)
> to teach or demonstrate the making or use of ... or to distribute ... information pertaining to ... the manufacture or use of an explosive, destructive device, or weapon of mass destruction
> ... with the intent that the teaching, demonstration, or information be used for, or in furtherance of, an activity that constitutes a Federal crime of violence
(B)
> knowing that such person intends to use the teaching, demonstration, or information for, or in furtherance of, an activity that constitutes a Federal crime of violence
Note that this very narrowly applies only when intent can be demonstrated, at which point you are arguably an active participant in whatever crime is being committed. In my opinion, that is quite different from your earlier claim.
> The US has plenty of laws against the use of speech to promote violence.
This isn't regulating mere promotion, it's regulating a form of active participation. The Christchurch Call agreement isn't even remotely similar.
Distributing such instructions with the intent to further a crime makes the speech unprotected. But, each element (e.g, knowingly intending to further a crime, and so on) has to be proven in a court of law to strip the speech of its protected status.
From the statute you linked: "...with the intent that the teaching, demonstration, or information be used for, or in furtherance of, an activity that constitutes a Federal crime of violence;"
edit: typos
https://www.law.cornell.edu/uscode/text/18/700
However, this act was explicitly ruled to be protected political speech under the First Amendment:
https://en.wikipedia.org/wiki/United_States_v._Eichman
In a similar vein, the law you've linked to would still be subject to the "imminent lawless action" analysis, were someone to be charged under it.