WASHINGTON — “I love you, China. My dear mother,” former U.S. President Donald Trump, standing in front of a mic at a lectern, appears to sing in perfect Mandarin. “I cry for you, and I also feel proud for you,” Vice President Kamala Harris, Trump’s Democratic opponent in this year’s election, appears to respond, also in perfect Mandarin. Trump lets out a smile as he listens to the lyric. The video has received thousands of likes and tens of thousands of reposts on Douyin, China’s variation of TikTok. “These two are almost as Chinese as it gets,” one comment says. Neither Trump nor Harris knows Mandarin. And the duet shown in the video has never happened. But recently, deepfake videos, frequently featuring top U.S. leaders, including President Joe Biden, singing Chinese pop songs, have gone viral on the Chinese internet. Some of the videos have found their way to social media …