Amazon isn't the only marker for overall consumer demand, but if Amazon has an item in stock, that does mean it's available in that market, nationwide. Granted, everyone doesn't buy from Amazon, but there isn't much of an argument for an item being "unavailable" where they live if they could order online.
My personal take on the stock availability: post Japan launch should mean more units are being re-allocated to alternate markets.
I won't claim to know what percentage of overall production yield was withheld for the Japan launch (3.5m units allocated), but I'm assuming current production rates of about 1m units per month for all markets.
I'd like accurate data on production rates since all I have to work off of are the number of units sold per month, but I seem to remember hearing 1m/month production rates last year.
When I start seeing PS4s on shelves at retail, then I'll take that to mean that initial demand is finally being met. I saw the first PS4 sold at retail last night; the first one I've seen "in the wild." It was being picked up by the customer at customer service, presumably placed on hold.







