Sofia Mattsson, despite being mostly recognized as an American star, was originally born in Stockholm, Sweden, and holds Swedish nationality. Although acquiring U.S. citizenship is a challenging process, Mattsson successfully accomplished it in 2022, sharing the news on her Instagram account. In a caption under a smiling photo of herself holding the American flag, the star wrote, "I'm so grateful to this country for all the opportunities I've been given and for helping me make my dreams come true."

The specific details of how Mattsson obtained her citizenship remain unclear. Typically, US citizenship can be acquired through either birth or naturalization. Since Mattsson wasn't born in the U.S. she had to have gone through the naturalization process, which requires residing in the United States for at least five years, according to USCIS, or being married to a U.S. citizen for at least three years before applying. Mattsson tied the knot with Thomas Payton in 2016, a fellow entertainment industry professional engaged in acting, writing, and producing. Given their nearly six-year marriage in 2022, it is most likely how Mattsson successfully navigated the legal procedure.

Many, including her fellow "General Hospital" co-stars, took to the comment section of Mattsson's post to congratulate her. Kathleen Gati, who portrayed Liesl Obrecht on the daytime drama, wrote, "Congratulations! I got mine in 2001. It's a great feeling!"