Why are there so few Sephardic Jews in the United States?

Hello, I am a Sephardic Jew living in the states. My grandparents on my mom’s side are Moroccan (emigrated to Israel when it became a state) and my grandparent’s on my dad’s side are Turkish (emigrated to the US). Whenever I introduce myself to other Jewish groups they tend to be surprised when I tell them about my heritage. What is the reason so few American Jews are Sephardic? Is it just because more Ashkenazic Jews emigrated to the US in the past? Did most just decide to move to Israel and stay there? I did some research but I couldn’t really find any definitive reasons why their is such a large disparity in the US.