Doing that when building these devices at scale and handling support queries for it is probably not cheap. Most phone manufacturers don't allow retailers to tamper with the software on the phones/tablets (that opens up a can of worms in terms of security), so they'd have to do it very early, maybe even at the factory — which means earmarking which devices are bound to Utah. Responsible manufacturers (e.g. Apple) would also have to audit the filter code, or build it themselves.
It gets even worse for Utah, though. The bill demands that any device activated in Utah comply with the law — not merely sold in Utah. So manufacturers would need to turn on location tracking and make it impossible to disable, for all users in the world, just to detect the corner case that they happen to be in Utah, so that they can silently turn on a Utah-specific porn filter.
I doubt the bill will pass, but if it does, I doubt many manufacturers would comply.
