The United States is not isolating Russia so much as it is isolating the West. From Thierry Meyssan at lewrockwell.com:
The Western sanctions against Russia, decided unilaterally by Washington, are presented as a just punishment for the aggression against Ukraine. But, without mentioning their illegality under international law, everyone can see that they do not reach their target. In practice, the United States is isolating the West in the hope of maintaining its hegemony over its allies.
The United States, which was a late participant in the World Wars and suffered no losses on its territory, emerged victorious from the world conflicts. Inheriting the European empires, it developed a system of domination that made it the “world’s policeman. However, their hegemony was fragile and could not resist the development of large nations. As early as 2012, political scientists began to describe the “Thucydides trap” by analogy with the Greek strategist’s explanation of the wars between Sparta and Athens. According to them, China’s rise to power also made a confrontation with the United States inevitable. Noting that, if China had become the first world economic power, Russia had become the first military power, Washington decided to fight them one after the other.