It's not like you just localize some webpages and add a currency option to your payment.
You've got to deal with certification, taxes, customs, warehousing, shipping partners, warranties, refund, and all with wildly varying levels of government agency cooperation and efficiency.
Apple is the only consumer company I know of who does this well, because it's their main business and they have the money and have gigantic teams of people who do this as their main job. And even then people complain about the sometimes vastly higher worldwide prices.
Now Google obviously does manage to eventually get these products out internationally. But it's pretty understandable that they sell in the US as soon as they can, and also can't necessarily predict the exact date they'll be available elsewhere.
(And yes you can work with local distributors, but that doesn't solve all problems, presents its own set of complex challenges, and sometimes may simply not be economically viable -- e.g. their cut will make the product non-profitable, and there isn't a market to sell at a higher price.)