He imitated the American accent down to the slightest inflection, though maybe the nasal sound was a little overdone, sounding more like a Chinese with a cold and a stuffy nose, rather than an American speaking.
他仿美国人读音,维妙维肖,也许鼻音学得太过火了,不像美国人,而像伤风塞鼻子的中国人。
a diacritical mark (~) placed over the letter n in Spanish to indicate a palatal nasal sound or over a vowel in Portuguese to indicate nasalization.