Actually the Italian population is 59 millions, not 40, there is a big difference. Anyway immigration just to have more available football players is one of the most ridiculous things I've ever heard. You get good football players having a clear project, having infrastructures, training facilities, good coaches, etc etc. Based on what I read here it simply looks like that a country needs more people, then explain why China and India are so bad that they can't even find 11 good players with more than 1 billion people each...
I will give you a very simple statistic.
In 1990, the population of 15-25 age group in Italy was close to 10 million. According to the census, as of 2025 this has declined to around 4-5 million. Total population keeps on growing. But the player pool is getting reduced.
Now compare the situation with Uzbekistan, who recently qualified to the world cup. In 1990, they had 2 million people in the 15-25 age group. As of 2025, this has increased to 6 million.
What I am trying to say is that demographics will have an impact. The argument with China/India is not suitable, because in these countries football is not very popular.