Why should the US take the lead in anything? Why should anyone look to the US for anything? If the current administration wants to remove tax subs for wind and solar and remove environmental regs for coal, then so be it. If the administration wants to tax Netflix out of existence to bring back Blockbuster, so be it.
Does the current administration have the balls to step up to an expanding China, or Russia?
If Russia made a move on Europe (Putin hates NATO and the EU, both targets of Trump rage), would the US step in? If China made its move on Taiwan, would the US step in? Should it? Could it?