Commentary President Joe Biden’s UN speech on Sept. 22 showed yet again that he has spent so long in the trenches of partisan political conflict that even as the president of the United States, speaking to the world ostensibly on behalf of his country, he can’t help seeing everything beyond our borders (such as they still are), as well as everything within them, in terms of domestic politics. For just as he couldn’t rise above partisanship to take responsibility for his actions as president and commander-in-chief of the Afghan debacle but tried to blame it all on Donald Trump, so it appears that he can imagine no role for America in the world apart from repudiating what he sees as the Trump legacy wherever he finds it. But then I suppose that the old rule about politics stopping at the water’s edge has been a dead letter for a couple …