In terms of research, it's been roughly true since WWII. Persecution by the Nazis and the war drove the cream of the European scientific establishment to the US

In terms of research, it's been roughly true since WWII. Persecution by the Nazis and the war drove the cream of the European scientific establishment to the US, and the US poured a large amount of government funding into science funding after the war. Things are changing, first because the European scientific community has recovered and also because scientific research has been taking off in Asia.