If the Republicans go “America First”, it means that the Israelis, the Europeans (not just the Ukrainians), the Taiwanese, the Philippines and the Koreans all end up under the bus. Depending on how overbearing the Russians, Chinese and Iranians are, the US might settle to except their domination as long as we are largely left alone domestically, or perhaps the US will quickly realize it made a big mistake, and go full force into a World War (as happened on the afternoon of Dec. 7, 1941).
But if you pay close attention to what Trump is saying, he has so far said he will only help allies who help themselves, and since almost all of the NATO members as well as the threatened countries in East Asia are seriously increasing their armed capacities themselves (even Germany is getting ready to go nuclear, we are thrilled???), Trump could simply take credit for global rearmament and become a reincarnation of Harry Truman, John Kennedy or Ronald Reagan. With Trump you never know.
And Biden may be so scared of losing the “WOKE” Democrats, that he’ll be steadily be turning into an anti-war, and anti-Israel Democrat.