It won't change the numbers that much. You can take a look at countries that are 99%+ native/Caucasian in Europe and they have similar numbers (roughly around 100).
Genetics accounts for about 75% of IQ, there's little to know argument about this. You could also argue that why hasn't IQ gone up in countries in the Middle East (UAE, Qatar, Kuwait, Bahrain, Saudi Arabia) when their "fortunes" have turned around completely. To me it's quite clear that countries with higher IQ populations create better conditions, not vice versa. My theory is that if you cleared up a country in Africa of natives, replaced with East Asians, that country would be relatively wealthy within 1-2 generations. Over time the evolutionary pressure for higher IQ might ease up and fortunes might dwindle but that's a longer process.
Baltics or Poland for example. It's changing but it's still about the same. You could also look at Finland 20 years ago.
Saint Lucia boasts the second highest ratio of Nobel laureates produced with respect to the total population of any sovereign country in the world. Two winners have come from Saint Lucia: Sir Arthur Lewis won the Nobel Prize in Economics in 1979, and the poet Derek Walcott received the Nobel Prize in Literature in 1992.