I am 100.0% certain that is incorrect. Loads of U.S. "rocket ship" owners have only a PPL - they can fly VFR right up to base of Class A which is 18,000 feet, and getting CAS transits out there is generally very easy. A large % of U.S. private pilots have an IR (of the order of 20% - about 20x more than in Europe) but the majority haven't.
Interesting that at least two rental outfits in the US that I know of insist on an IR for the SR22 but not the SR20. Bizarre.
The SR22 is dead easy to fly - yes it is a quicker then nearly every other single - if you want it to be, and yes, the glass takes a bit of getting use to if you are new to glass and yes - it is slippery, so you need to think about more about slowing it down - but that is about it.
If you are use to a fast(ish) complex single and glass it is a doddle - if you are not the speed and capability of the aircraft could well get you into a whole heap of trouble.
I am not sure the under carriage is that much of an issue. I would be interested to know how much saving there could be in fuel burn but given the economies of scale of "investing" upwards of £300K in an aircraft and saving a few gallons of fuel an hour I doubt it is a factor for most. Moreover, their biggest market is the States by far where, rightly or wrongly, the insurance firms dont like anything other than welded uncarriage and Avgas is half the price.