Not all sonnets are the same. The Italian sonnet is also known as the Petrarchan Sonnet and people usually refer to the English sonnet as Shakesperian sonnet because of how Shakespeare popularized sonnets in the past. Take note that the writers did not develop the sonnets on their own. They were the ones who made the use of sonnets popular in different parts of the world.
There are also some differences with the structure of the sonnets. The Italian Sonnet usually has two parts while the American sonnet can be divided into three parts but remember that all sonnets have 14 lines. The Italian sonnet was created first then the English sonnet.
The sonnet is the most universal of all kinds of poetry because It has a particular pattern of rhyme and meter. It can be found in two forms like Italian and English sonnets. English sonnets were popularized by William Shakespeare, whose most famous sonnet is the love story of Romeo and Juliet. Michelangelo popularized the Italian sonnet. The two parts of the Italian sonnet are the octet consisting of eight lines which tell us the problem and the sestet, which consists of six lines that provide the solution to the problem.
On the other hand, the English sonnet consists of three quatrains and a couplet, while the volta signifies a shift in the poem. The volta is located in the third quatrain of the English sonnet, although it is located in the ninth line of the Italian sonnet. The most significant difference between the English sonnet and the Italian sonnet is its rhyme scheme.