AFAIK literally no contemporary US politician but Trump has ever entertained the idea of annexing another country, but I have zero confidence that anyone around him would do anything but roll over if he gave the order. He isn't just pretending to be crazy for galaxy-brained game-theoretic reasons, he literally is crazy and unpredictable and surrounded by shameless enablers. Even though the military would be legally obligated to refuse an unlawful order from him, I no longer have any confidence that they actually would.