I don't think insurance companies even offer that much for normal policies in the US. Maybe if you're insuring a Veyron, but otherwise that just seems insane to me.
The most my insurance company even offers on a normal policy is 300/500/100 and when I asked about it my agent said it was excessive and that no-one needed coverage that high. When a guy who works on commission tells you that you'll never need the higher priced option, that says something.
ZV
Yeah, the American standard seems to be to get umbrella coverage if you need to go that high. I guess if you live somewhere that you can expect to crash into 5 $1M cars, or plan on running your tank through someone's garage, living room, bedrooms, and kitchen, then the $5M for replacement of house may come into play.