The answer is number 3: The eagle represents the threat the United States poses to other countries
This cartoon, published in 1898 in support of US expansionism, was named "Ten Thousand Miles From Tip to Tip", referring to the extension of United States from Puerto Rico to the Philippines.
It was published in the Age of American Imperialism, a period where the United States acquired lands crossing from the Philippines to Eastport, Maine, and the country was being a major political, economic and cultural influence beyond its borders.
Giving the context of the period and the eagle's stance, with its outstretched and large wings over the possessed lands, the eagle symbolizes the U.S. as an imperialistic power, protecting its lands below, and with the threat to become a global power, superior to the rest of the countries.