In the US, relationships don't matter as much. They still matter for your career, but someone will do business with you as a way to start a relationship. In many places, the relationship is a prerequisite to doing business. If you don't have the relationship, you can usually just pay a bribe.

I wouldn't try to link the US' foreign policy to our cultural norms. Foreign policy exists in the realm of realpolitik, and every rational actor would likely behave the same way if they were in the US' place. When it comes to setting the global balance of power, anything and everything is fair game. This is why presidents customarily don't criticize those who come after them.