America the Beautiful was originally written as poem to celebrate America's Independence. By iteration the poem was refined to the popular version we know today.
It better represents America's ideals, and being easier to sing it is frequently preferred over The Star-Spangled Banner. It speaks to the grandeur of our nation, bounty, liberty, freedom, patriotism, and our debt to our founders wisdom to create a nation that could improve on what they created.
It was not until 1931 that a congressional resolution established an official anthem. Prior to that point, "Hail, Columbia", "My Country, 'Tis of Thee" were among several patriotic songs that were employed during the display of the American flag.
As this was established by resolution and not law, it is easily amended.