re: Why should the U.S. be an enemy of modern day Russia?

US global hegemony is underpinned by preventing a Eurasian superpower from developing, and the US Navy’s unchallenged dominance over the global oceans / seas. The two are related: the only thing keeping Russia from achieving the ability to threaten us is it’s lack of access to warm water ports.

Should a power such as Russia achieve its objective of securing permanent, stable ports from which a significant Navy could be deployed / supported, it’s a direct threat to us. Otherwise, NATO is a waste of time, and we could just let them have Europe at limited geopolitical cost.