People rally against zealous lockdown of PC (recently restricted boot in EFI, earlier TrustedComputing in general). Not being able to install any software of choice (with reasonably little effort) sure is bad, but having an already functioning computer swept right from under your fingertips could easily be way more damaging. Government couldn't do that without serious due process. Why a company can, and why aren't there voices of stern protest?
That's nonsense - look at the hours of merchandise promotion across dozens of channels. Toys is billions of dollars per year.
Is a parent going to look at untargeted (because of COPPA) gmail.com advertisements while their kid bangs out the odd email? No.
The point of targeted advertising from Google is to show you a relevant ad during the few times that you use their app. With COPPA, all of this goes out the window.