Final answer:
China accounts for the highest portion of worldwide military spending excluding the U.S.
Step-by-step explanation:
The country that accounts for the highest portion of worldwide military spending excluding the U.S. is China. According to the International Institute for Strategic Studies for 2018, China's military budget was the highest among the given options, surpassing countries like Russia, Britain, France, and Germany. China has been consistently increasing its military spending in recent years, reflecting its growing military capabilities and global influence.