According to the Times Higher Education World University Rankings 2015/16:
Australia
22 of 40 Australian universities are in the world's top 400 - those 22 universities enrol 65% of Australia's university students. 65% of Australia's 1.3 million students are in universities in the world’s top 400.
USA
112 of over 3,000 four year degree granting institutions in the USA are in the world's top 400 - those 112 universities enrol 20% of America's 13.4 million students. 20% of 13.4 million US students are in universities in the world's top 400.
UK
46 of 161 UK universities are in the world’s top 400 - those 46 universities enrol 33% of the UK's 2.3 million students. 33% of 2.3 million UK students are in universities in the world’s top 400.
Just one way of looking at the rankings results.
Australia
22 of 40 Australian universities are in the world's top 400 - those 22 universities enrol 65% of Australia's university students. 65% of Australia's 1.3 million students are in universities in the world’s top 400.
USA
112 of over 3,000 four year degree granting institutions in the USA are in the world's top 400 - those 112 universities enrol 20% of America's 13.4 million students. 20% of 13.4 million US students are in universities in the world's top 400.
UK
46 of 161 UK universities are in the world’s top 400 - those 46 universities enrol 33% of the UK's 2.3 million students. 33% of 2.3 million UK students are in universities in the world’s top 400.
Just one way of looking at the rankings results.