It's not a market of 512M, it's many small markets of different languages and different cultures that all need to be targeted individually whereas the US is actually a much larger market of a single culture. Focusing on the big mono language mono culture market instead of chasing dozens of smaller markets that require much more effort in internationalization is actually good business advice.
It is a single market. That's the whole point of the EEA.
Your personal interpretation of the situation is irrelevant.
From a business standpoint trying to market goods, no, it isn't. That's just a fact. Every culture has to be marketed to differently, they are different markets.
US is actually not a single market. At least, not as much as you'd like to believe.
There are regions, but they all speak the same language and use the same date formats: you do not have to internationalize or target your app, it is thus a single market. Not remotely so in the EU.