Why is the US pointed at as the reason for their culture loss?
Because the US is the biggest exporter of culture in the world. It's not a secret that since WWII the US understood the concept of soft power and that culture projection is a big part of it. It's good for the diplomacy, it's good for the economy (everybody wants to resemble the americans, listen to their bands, wear their gear, etc.).
It's also very annoying, mainly because it brings uniformity. And because, yes, it crushes other cultures in its path. Not willingly, more like Walmart kills small retailers.
"The medium is the message." -- Marshall McLuhan