A simile is a figurative language that uses comparisons to describe an event, someone, a place, etc., while using the words "as" and "like" to make the comparison, and similes are often used with the purpose of making the writing more colorful and interesting. The statement demonstrates a simile because it compares the way old fears cling to the way cobwebs cling while using the word "like."
It had a negative impact on the Native Americans, because the settlers were taking over the Native's land and livelihoods. As more Europeans came, the Natives were forced further and further from their tribal lands.