The Absence of a Pronoun Antecedent

An online local news provider reported about the same-sex marriage and went:

... This came amid news that New York City has also legalized gay marriage. It became the sixth state in the United States to do so.

There are two things that are wrong in this sentence.

1. The pronoun It in the second sentence does not have an antecedent. The pronoun does not clearly point to New York City.
2. If the It pronoun does point to New York City, then it negates the succeeding thought, which is "the sixth state in the United States..." New York City is not a state. There is a New York state of which New York City is a part of. 

Be careful with your pronoun antecedents and facts.