Maintaining national unity in a liberal democratic state is far easier in the face of a compelling, dangerous external enemy. I don’t think it is a coincidence that politics in this country started to become more polarized shortly after the demise of the USSR. So what could replace the Russians in the foreseeable future?
It could have been, and should have been, the virus. If Trump had possessed an ounce of sense and intellectual flexibility, he would have worn a mask and made fighting the virus an overriding national priority. Americans would have responded favorably even if he had failed. He didn’t try, however, and the rest is history.
The Chinese? Maybe. Getting tough with them is popular with both parties; to the extent that China is a partisan issue, it involves means, not ends. The question is whether Trump has already irrevocably divided us on foreign policy. That remains to be seen.