How do you evaluate the results of Guan Yu's Northern Expedition? Why is it said "Megatron China"?

The world at that time could not just look at Guan Yu's battle in Fancheng, Xiangyang. Since Cao Cao's defeat in the Battle of Chibi, the front army commander Xia Houyuan was beheaded in the western region, and the strategically important Hanzhong was captured. In the southeast, the Sun Wu regime has been eager to try Hefei. From the due south, Guan Yu tried his best to attack Xiangyang, intending to capture the Nanyang Basin and then use it as a springboard to enter the Central Plains. It can be said that since the Battle of Chibi, Cao Cao's foreign strategy has been passively defensive, except for occupying Hanzhong in the western region (which was captured by Liu Bei before his butt was still hot). Therefore, Guan Yu flooded seven armies and surrounded Xiangyang, which greatly affected Cao Cao, because once Xiangyang was captured, it was equivalent to tearing a hole in the battle line, and Cao Cao even wanted to move the capital to avoid its edge.

So it is not a lie to say that Guan Yu was powerful in China at that time