Americans only work harder only WHEN IT IS IN THEIR SELF INTEREST TO WORK HARDER. That is what capitalism is all about. American socialists are trying to change that formula. American people of all races, religions and creeds are not stupid.
There’s a bit more to it than that for a lot of people.
“Greed is Good”
“Greed Works”
The problem with most of these European countries that they are taxed at such a high rate that there is less incentive to work hard, take risk and be an entrepreneur.