There is no one big "startup nation". In fact, there are many countries around the world with thriving startup ecosystems.
Some of the most notable startup ecosystems can be found in the United States (Silicon Valley in particular), Israel, Singapore, Sweden, and Finland. All of these countries have achieved success in fostering an environment that is conducive to startups and entrepreneurship.
There are a number of reasons why a particular country may be more successful than others in terms of startup activity. One reason may be the availability of capital. Venture capitalists and other investors are more likely to invest in a country that has a proven track record of success in terms of startups.
Another reason may be the presence of a strong talent pool. A country with a large number of highly-skilled workers is more likely to produce successful startups. This is often linked to the education system in a country – if students are taught to be creative and innovative, they are more likely to become successful entrepreneurs.
Finally, a country's legal and regulatory environment can also play a role in determining startup success. A country with laws and regulations that are friendly to startups and entrepreneurs is more likely to see a thriving startup ecosystem.
There is no one-size-fits-all answer to the question of which country is the startup nation. The success of a startup ecosystem depends on a variety of factors, and each country has its own strengths and weaknesses.