On a gdp basis, which heavily favours the US, the US is not even the top dog. It's just above Belgium and below South Korea.
replyAbsolute values would favor the US, not a percent of gdp.
replyYou're comparing the sum of those European countries to the US.
replyScientists have two easy avenues if they are currently in the US, the US or their home country. Immigration to work in a foreign nation is not always easy and takes time.