According to this web site https://ourworldindata.org/coronavirus#coronavirus-country-profiles the total number of tests in the US up to today is around 28 M. They do not give numbers for the EU as a single entity, but when you add up the numbers from individual countries you get 14 M for Germany, Italy and Spain combined. The four most populous countries in the EU are these three plus France; data for France seem to be missing. Germany, Italy and Spain have a total population of 190 M, compared to 330 M for the US. Thus, I would say that the percentage of the population that has been tested on both sides of the Atlantic is similar.