Because there are more iPhones in America.

Ignore that Apple also makes it impossible to side load apps.

Apple was the canary in the coal mine for this behavior in the EU. Apple was forced to allow third party apps, so Apple mandated that everyone had to register with them, and pay them their yearly fee, and then developers had to pay Apple another fee (core technology fee, still double dipping), and governments were completely fine with that. (And developers will happily jump through more hoops to develop on iOS).

Google saw this and decided if they can, so can Google. And this technically is the easier of the two as at least this doesn't require every developer to register with Google this way.

Doesn't matter when the CEO sits at the table with the US president. If it's illegal it won't be enforced. Or it'll be made legal. Or it won't be made illegal. And if you want to make it illegal in your country - there's punitive tariffs coming your way from the US president.

The public institutions responsible for tearing apart monopolies would have a field day with google if they were even remotely as powerful and willing as they used to be.

Because there are alternatives. No one is forcing you to use Android.