Not really saying otherwise. What I am saying is that for your electronic devices to have “explosives” in them would require that a supplychain attack of a similar sort.

It’s almost definitely not the case that any electronics manufacturers are systematically putting explosives in every smartphone or whatever that they manufacture and supplychain attacks are much more likely to be a targeted thing rather than “all Samsung phones” or whatever. If they weren’t targeted, it’s pretty certain that the presence of explosives in devices would be noticed even just by regular end-users with a bit of a tinkering proclivity within weeks. So if your devices are more than a couple of months old have been in reasonably normal use for most of that time and you haven’t been specifically targeted by any particular government or anyone who might have the ability to tamper with the supplychain, you’re almost certainly safe specifically from explosive-laced consumer electronics devices.

Also, it seems unlikely that a state police agency (like the “sheriffs” you’re talking about) could leverage enough power to compel an electronics company to allow such a thing without the FBI or DHS involved. I’d imagine state police folks would more likely resort to more low-tech approaches like the Tulsa race massacre air firebombing.

Again, I’m not saying it’s impossible that your phone contains explosives. And as I said in another comment, it might be possible to remotely get a device to cause its battery to catch fire. Maybe.

Also, I am in the U.S., but what made you think that was the case?