Why are American DIY shows scary to British electricians?

Wire nuts.

Those things are hideous. Mains wiring should (a) use a real colour code (IEEE standard for example), and (b) be fastened VERY securely. Something like choc-block (a sort of screw-terminal in plastic strip thing, for americans who may never have come across it), not a naff little bit of plastic and metal that screws onto the twisted together wires and holds it in place more by the grace of god than anything else.

I've done quite a bit of wiring in North America, and a hell of a lot in England, and I know which I think is safer. Wire nuts, cables stapled in place with nasty, very sharp metal things you hammer in across the wire with only a little bit of cardboard to insulate it, and predominantly wooden houses is a situation begging for a disaster.

Several electrical-type engineers I know across the pond say I'm being prejudiced, but do admit they seem to see a lot more house fires caused by electrical faults than we get over here.

I remember servicing an imported coke machine a few years ago at a job I had at the time, and after taking the cover off just staring in disbelief, afraid to touch it. I have no idea how it was inported, but I can guarantee it wouldn't pass european safety directives. The health and safety people would have had a nervous breakdown if they'd ever inspected it internally.

Nasty, nasty, nasty wire nuts.

pca