The Grammy Awards are presented by the Recording Academy, formerly known as the National Academy of Recording Arts and Sciences. Founded in 1957 as an American organization, it would stand to reason that it would be American focused. The Cold War would have eliminated much of Europe, China was still closed, Rock was still in its infancy, worldwide distribution was still relatively new, ... there were many political, cultural, technical, and other deterrents to entries from outside the country, and even those would likely be music in English.
In more recent years, the Recording Academy has shifted toward viewing itself as a worldwide organization.
The 63rd Grammy Awards Rules and Guidelines do not specify any restrictions on the origin of the music or performers other than recordings generally must be "new" and available nationwide. However, the music must be released in the United States: "imports are not eligible."
“New recordings” is defined as material that has been recorded within five years of the release date and not previously released.
GENERAL DISTRIBUTION: “General distribution” is defined as the broad release of a recording, available nationwide via brick-and-mortar stores, third-party online retailers and/or streaming services. (Imports are not eligible.)