かぶれる (kabureru) is a standard Japanese word that means that one’s thoughts have been overly influenced by new ideas, especially the culture of a specific foreign country. Those people who are too fond of a foreign culture are called “~ かぶれ”, e.g. “アメリカかぶれ (America かぶれ)” means “American-phile”, i.e. those who are overly influenced by the American culture. They tend to have a very shallow understanding of the culture, and possess very biased and overly generalised thoughts about the country, such as “Everyone in the U.S is very positive and enjoys their life, but people in our country are always depressed and gloomy”.
Although not used among Japanese people, you may also say “日本かぶれ (Japan かぶれ)” to indicate a “weeaboo”, a person who is obsessed with Japanese culture.
Since he studied abroad in the U.K., he has been really かぶれてる (overly affected by the British culture)
People who eat beef are 西洋かぶれ (overly affected by western cultures, western-phile).
(note): This is said to have been a once widely accepted thought in Japan at the beginning of the Meiji era, 1800s.
Synonyms in English: be obsessed, be influenced, fanboy, ~phile
Related words and phrases: かぶれ