It doesn't matter if it's American or anything else, when one culture is adopted entirely, the one that was holding its place deteriorates. That's just basic logic. Other parts of the world are how they are because of what surrounds them, the landmarks, the food, the music, the people. When you stop looking inward at them and look outward for identity, what's around you changes.
I love the United State of America. It is a wonderful country. With that being said, it is not the only way to live. It is wrong to try to force the rest of the world to adopt to our ways. Adopting to American ways would decay unique international cultures. There is no reason to force our way on everyone else. People should choose for themselves.
It is perfectly reasonable to expect that maximizing individual freedoms actually encourages the maintenance of all cultures, if those cultures want to keep them alive.
At its core, the constitution of the US is the most free set of rights in the world. While the country has its issues, those freedoms explicitly allow for people to do what they want, including maintaining their 'unique international cultures' provided those cultures do not infringe on the rights and freedoms of others.
Could it be better? Sure. All nations could do a better job of supporting such things. But maintenance of culture should be the work of the people.