The eagle has carried both national and spiritual meaning for centuries — a symbol of the United States since 1782, and long before that, a biblical image of strength and renewal, most famously in Isaiah 40:31: "They shall mount up with wings like eagles."
Pairing an eagle with a cross links both meanings at once — national identity and spiritual renewal in a single image. You'll see it across pieces like Eagle Cross — They Will Soar on Wings Tee and Eagle & Cross Isaiah 40:31 Tee.