It takes a huge critical mass (read : deep pockets) for any non-European company to be able to market their products in "Europe". Whereas in the US, it may be possible to reach a huge audience by advertising in one or two major Running magazines, in Europe, each country would have its own magazine....or even several, in individual languages within one country. So above-the-line advertising may get prohibitly expensive very rapidely. Hence the GS products remain relatively unknown.
It's very difficult to make that concept clear to US Marketeers :-) I can tell, it's been my job for the last 25 years :-)