This is exactly what the study shows is not just possible but easy in screening by nationality. Think about US immigration statistics by country (https://en.wikipedia.org/wiki/Immigration_to_the_United_Stat...): you'll see lots of Central and South American countries. Now take a look at what the study finds (http://nfap.com/wp-content/uploads/2016/03/Immigrants-and-Bi...):
"The leading country of origin for the immigrant founders of billion dollar companies was India with 14 entrepreneurs, followed by Canada and the United Kingdom with 8, Israel (7), Germany (4), China (3), France (2), Ireland (2) and 12 other countries with one entrepreneur.2
India: 14
Canada: 8
United Kingdom: 8
Israel: 7
Germany: 4
China: 3
France: 3
Ireland: 2
Armenia: 1
Azerbaijan: 1
Argentina: 1
Egypt: 1
Holland: 1
Iraq: 1
Norway: 1
Russia: 1
Singapore: 1
South Africa: 1
South Korea: 1
Uzbekistan: 1"
Does this look remotely like current US immigration? It does not. (Hey, you know what countries I don't see on that startup founder list? Mexico, Philippines, Vietnam, El Salvador, Cuba, Dominican Republic, Guatemala, Jamaica, Colombia, Haiti, Honduras, Peru, Ecuador...) If you were building a model to predict startup founding by nationality and personal details like IQ or ethnicity (no prizes for guessing what ethnicity that 1 South Africa founder is, or what religion that 1 Iraqi founder is), and designing immigration policy around that, it would look nothing like what has gone on for decades.
Using startup founders as an argument for the status quo of illegal immigration is a deeply dishonest bait-and-switch piece of equivocation (see https://en.wikipedia.org/wiki/Fallacy_of_division ) and it makes my teeth grind every time I see someone go 'did you know 50% of startup founders/CEOs/scientists are immigrants?' Justify it on its own merits, don't pretend that Indian brahmins and Israeli Jews' accomplishments have anything to do with not building a wall along the Mexican border!
This is a very similar fallacy as the 'US has only 5% of the world population, therefore it only has 1 out of 20 of the best researchers/programmers/entrepreneurs' (most recently seen on Paul Graham's Twitter). This is not remotely the case because of differing health & political & economic & scientific development & mean IQ, and the further out on the tail you go (such as 'best programmers in the world') the more lopsided the global distribution becomes - much the same way that women make up 50% of the population but do not make up 50% of people over 7 feet tall or the NBA.