I've heard this claim before and see no evidence for it in any Egyptian texts or iconography. Acharya S is unscholarly, makes many silly mistakes, and thus is unreliable; and Maher's people obviously got his bullet points from the Acharya piece to which you linked in your question.
Acharya throws up numerous points hoping that some of them will stick, but they don't. She doesn't cite any Egyptian texts that support her view, which is not surprising because there are none and, I would argue, there can be none. This is because the idea that Horus can be crucified and resurrected is logically precluded by Egypt's mythology and religious thinking. While a person is alive (taking the king as the example), he is Horus. But once you die, you become Osiris and are not Horus, so it can only be Osiris who is resurrected.
Not having any Egyptian texts to rely upon, Acharya relies on images of Horus with his arms out from his sides, and the idea that the Egyptian ankh and Christ's cross are the same. See this article: Was Horus "Crucified?" However, the ankh sign comes not from a cross but from a sandal strap (see Gardiner sign S34). In Egyptian, the ankh glyph is used to mean "life" as well as for the verb "to live," but it never is an agency of death; in Egypt no one ever dies on an ankh, much less is crucified on one. There are no such images in the iconography, since crucifixion was not practiced in ancient Egypt (at least before Roman times).
Further, a figure holding out his arms in itself says nothing about death or crucifixion, or a cross or Christ. Acharya's notion reminds me of Tertullian's laughable interpretation of Moses' surveying the Hebrews' (led by Joshua) battle against the Amalekites (Exod.17:8-13), where by standing on a hill and surveying the battle below, Moses (with help from Aaron and Hur) held his hands out to his sides and so caused the Hebrews to prevail. Tertullian claimed that this posture prefigured Christ and the cross, foretelling the cross through which Christ would be victorious over death and bring salvation. (Tertullian, Against Marcion, Book 3, Ch. 18.) No one would agree with such kinds of interpretations today. Yet Acharya relies on similarly ignorant/silly statements and wishful thinking by Church Fathers to support her claim.
In the past it has sometimes been claimed (e.g., by Wallis Budge, in his Legends of the Gods (1912), see this article; THE LEGEND OF THE DEATH AND RESURRECTION OF HORUS, AND OTHER MAGICAL TEXTS. (Among Egyptologists, Budge is no longer considered reliable)) that, in a myth recited on the Metternich Stela now on exhibit at the Metropolitan Museum in New York, the child Horus is stung by a scorpion (which is Seth's doing), dies from the poison, and is resurrected by Thoth. But I know of no modern reading/translation of this text that has him dying rather than just unconscious and on the brink of death. The Stela's text itself says that "the child was weak beyond answering," and "refused the jar [of drink]," which obviously means he is not dead. J.F. Borghouts, Ancient Egyptian Texts (1978), p. 63 (in lines 171-74 if the Stela). The scholarly discussions of the text accord with this interpretation. See Nora Scott, "The Metternich Stela," The Metropolitan Museum of Art Bulletin 9.8:201-17 (1951) (Horus is "unconscious" (p. 213); Scott was Research Fellow in the Egyptian Art Department at the Met); John Nunn, Ancient Egyptian Medicine, p. 110 (1996) (Horus is "unconscious"); Robert Ritner, The Mechanics of Ancient Egyptian Magical Practice, p. 57 n. 266 (1993) (Horus is "injured"); Geraldine Pinch, Magic in Ancient Egypt, pp. 144-45 (1994) (Horus is "too weak and ill to suckle" and has a "sickness"); Emily Teeter, Religion and Ritual in Ancient Egypt, p. 175 (2011) (Horus was was "cured" by Thoth, which does not seem like a raising from the dead). This interpretation makes sense in terms of the magical spells recited that invoked this myth to cure victims of snakebite, scorpion stings, etc., who are still alive; they are not being brought back from the dead. For this purpose, the recovery of Horus was being used as a parallel example, so it made sense that he too was only on the brink of death. It is like the Billy Crystal scene in The Princess Bride, where his character Miracle Max observes that Wesley is "only mostly dead," and then proceeds to bring him back.
So, to put it bluntly, the idea is a load of Horuss**t.