Factors that affect green card processing times include which office processes the card, whether the application was submitted from within or outside the country and whether all the necessary documents and forms were submitted correctly. Additionally, whether a visa is available affects processing times, notes U.S. Citizenship and Immigration Services (USCIS).
Different field offices and service centers have different processing times, according to USCIS. For consular applications, processing times also vary by consulate. USCIS provides estimated processing times for field offices and service centers on its website at USCIS.gov..
In some immigration categories, visas are always available, while visas are limited for other categories. This can delay the approval process, according to USCIS.