Question

Applicants for naturalization a0 allegiance to the foreign countries of which they were formerly citizens.

Answer 1

Applicants for naturalization have to renounce their former allegiance. If you come from a country in Europe and would like to become a citizen of the US, you have to renounce your citizenship of that previous country. 

Answer 2

Applicants for naturalization RENOUNCE allegiance to the foreign countries of which they were formerly citizens

And they swear their allegiance to the United States in various aspect of his lives, whether it's economy, social, Accomplishments, etc.