The comment from UN ambassador Nikki Haley comes as President Trump spoke by phone with Japan's Shinzo Abe.
The internet is praising her pettiness.
President Donald Trump spoke to Japanese and Chinese leaders over a possible response to North Korea actions.
The dismal showing for Abe's party is also a stinging rebuke of his 4-1/2-year-old administration.
North Korea has tested several ballistic missiles that landed off Japan's coast this year.
Moon Jae-in has set out his plan to ease tensions on the Korean peninsula.
Japanese leader will discuss Pyongyang's spat with the U.S. over nuclear tests.
Health inspectors found the violations two weeks before Japanese President Shinzo Abe ate there.
At hate rallies, many have called for Koreans to "get the hell out of Japan" and that foreigners should "all be massacred."
The message seemed aimed at China, which claims almost all the South China Sea and which has fueled concern in Japan and the West with its growing military presence in the waterway.
North Korea fired four ballistic missiles into the sea off Japan's northwest coast on Monday, angering South Korea and Japan.
Japan's prime minister was the first world leader to meet with Trump after the November election.
The Washington and Florida meetings represent Abe's latest move to strengthen Japan's longstanding U.S. alliance in the face of China's rise.
Trump told a local sports radio station last weekend golf was a better way to get to know someone than lunch and saw his match-up with Abe as a "fun" meeting between partners rather than adversaries.
Abe has reportedly called for officials to gather "tweetable" figures on Japanese companies' investment plans—and is planning to play a round of golf with Trump.
Trump, who took office last Friday, reiterated on Thursday he would strike numerous bilateral deals, as opposed to multilateral accords like the TPP.