Is the Tang Dynasty’s Kaiyuan era more powerful than the United States today?

No comparison. During the Kaiyuan period, the most powerful empire in the world was the Arab Empire, and the Tang Dynasty could only take second place. The Xuanzong Dynasty was a period of change for the Arab Empire from the Umayyad Dynasty to the Abbasid Dynasty. It was also a period of rapid expansion. The Arab Empire's eastern expedition forces arrived in Central Asia at the end of the Kaiyuan Dynasty, and in July-August 751 AD, they conquered Talas. He fought with the Tang Army's Anxi Protector Gao Xianzhi and defeated the Tang Army. After that, the Tang Dynasty was forced by the Anshi Rebellion and gave up its management of the Western Regions and Central Asia. The Anshi Rebellion severely hit the Tang Dynasty and gradually declined. At this time, the Abbasid Dynasty became more and more powerful. Its long-term containment of Tibet near the Pamir Plateau was also a very important reason for Tibet's decline.

In the prosperous period of Kaiyuan, there were more than 8 million taxpaying households and a population of 54 million, plus the non-taxpaying population (including bureaucrats, nobles, gentry, monks, inward immigrants of ethnic minorities, Jisizhou counties, foreign businessmen), etc. It should be between 60 million and 100 million. Generally speaking, population can be used to illustrate the strength of a country. The number of taxpayers can most clearly demonstrate the economic strength of a country.

Comparable countries include the Arab Empire and the Eastern Roman Empire (Byzantine Empire)