The reasons are numerous. But they all come down to there being no basis upon which to have one. Let's review the essentials.
1) Russia poses little if any geopolitical risk to the United States or its vital interests. It is at best an irritant on the margins. Nowhere is this better illustrated than by the fact that almost the entirety of Russia's foreign policy is tied up with trying to solidify dominant relationships with the countries ringing its borders, almost all of which were part of the Soviet Union, their so-called 'near abroad'. Their success at this has been uneven at best. They are, so to speak, preoccupied with issues in their own backyard and show little sign that anything will change on that front in the foreseeable future. To the extent the US faces a challenge in its global primacy it is from China, with its expanding investments and diplomacy in Latin America, Africa and other parts of the world. But even that is almost exclusively economic. And that other thing - Russia isn't China.
2. Ideology. For three generations, the Soviet Union was the locus of an ideological movement that had a profound hold in Europe, throughout the Third World and to a non-trivial degree in the US itself. It was the backer or sponsor of communist movements and anti-colonial movements throughout the world, often with the two melding into each other. The US appointed itself as the power to hold the line against communist expansion. With the benefit of retrospect this was not the sole driver of the Cold War but it was certainly the organizing context of the Cold War and a critical driver of it. Russia isn't communist anymore. It represents no contrary ideology, other than a thuggish sort of authoritarian quasi-democracy which has little ideological draw anywhere.
3. The Army Thing. The Soviet Union, tied to causes 1 and 2, had the strongest rival military in the world with a massive land army poised against Western European countries the US was treaty-bound to protect from a Soviet Invasion. The US meanwhile lacked sufficient land forces to indefinitely hold off a Soviet Invasion which made it frighteningly reliant on nuclear weapons. The US had analogous commitments in the Middle East and obviously found itself involved, especially after the mid-60s, in various proxy wars in Africa, Latin America and Asia.
Nothing here is original. These are things we all know. And of course the bases of the Cold War include myriad reasons and tensions and drivers beside these. But these were the key drivers: global efforts to secure each side's zone of influence, unchecked and partly unstable military rivalry, and an ideological contest which divided much of the world. None of these are the case now.
Yes, Russia still has nuclear weapons. But in the absence of anything to fight about, they simply aren't the same kind of threat, other than the fact that it's sort of dangerous to have so many of them around in the world. Russia has the ability to bust our chops in our efforts to dominate and force terms on countries like Iran and Syria. But these are mainly irritants not threats.
At the end of day the Russia just doesn't matter that much in the early 21st century world, certainly not as an any sort of primary let alone existential threat to the United States. Constantly wondering whether there's going to be another Cold War is either based on ignorance or the continuing presence of people in the US who simply grew up with the Cold War and haven't ever been able to think outside of its constructs and thus, paradoxically, pine for it to come back.