what's the point of registering trademarks if by the very nature of using a mark affords you protection anyway?
That would depend on your country.
Registration confers a number of procedural and substantive advantages.
In the US, a registered trademark is presumptive evidence of the ownership and validity of the mark. You don't have to prove up the elements of a mark, because you have a registration certificate.
Common law rights depend on geography, and arise under state law. US Federal registration provides nationwide constructive use. For example, if I run a bakery in New Jersey and New York, I can obtain federal registration, and can use it to stop you from using the same mark in Hawaii. Without federal registration, if I had not been actually using the mark in Hawaii, you could go right ahead and use it.
Another advantage is that federal registration provides constructive notice to others of the mark. If I have a registration, and you are infringing, I do not need to prove whether you were aware of my mark - my federal registration provided you with notice (whether you looked at it or not).
So if they operate and market exclusively in the EU and are only a recognized brand there, can they expect protection in the rest of the world? If it's a domain name, is it not by default, a global usage?
I'm having a hard time putting those two questions together.
If they are not engaging in commerce in the US involving goods or services bearing the mark, they are not using the mark in the US. They may have a domain name, and their website may be accessible from the US, but so what? Having a domain name and an accessible website, without more, does not constitute use of a trademark in the US.
...and, again, in the US, trademark rights arise through use of the mark on goods or services in commerce in the US.