This. Even compared with the simplest BM Fighter 20, with archery fighting style, CBE/SS feats and then maxing out Dex, and a few fitting maneuvers incl precision attack, I can't see where the bard reliably catches up... oh wait, yeah, once it can do Simulacrum shenenigans with magical secrets.
Bard Archer's significant drawback in my book is that, since to be a good archer you need feats and prioritize dex, this means ignoring charisma and becoming a worse bard (less inspiration, less save DC's, bonus action for inspiration interferes with bonus action attack). If I'd go for a caster archer I'd prefer Hexblade (some nice invocations that improve your damage and BFC) or Battlesmith Artificer - both of them having the same to hit/damage stat as casting stat, and having ways to ensure you get at least a +1 hand crossbow (invocation/infusion, without having to spend limited resources, risk losing concentration and needing buffing rounds). But as other's have said, it is viable, most things are in 5e.