If backlinks were the sole reason, then many SEO-related keywords would be dominated by .edu and .org sites, but this isn’t the case. Over the years, Google’s algorithms have evolved. Initially, sites with high PageRank and many .edu links ranked well. However, Google improved its algorithms, focusing more on the context of links, the relevance of surrounding text, and the quality over quantity of links.
Due to these algorithmic changes, the sheer number of backlinks matters less. Links from multiple pages on a single domain count less, and the position and context of a link are more significant. Given these advancements, it seems unlikely that backlinks alone explain SEO-USA.org’s rankings.