Step-by-step explanation:
speaker identifies so strongly with the west wind because he wishes for his ideas to blow around the world with the same force that the west wind uses to scatter leaves around the earth.
The poem plays on the dual meaning of the word "leaves": the word refers both to the leaves on the trees that the wind blows and the leaves or pages on which the speaker writes. He desires that his leaves—his writing—be dispersed as widely as the autumn's leaves and that the west wind could blow them around the earth too. He writes:
Make me thy lyre, even as the forest is
What if my leaves are falling like its own!
The poem also plays on the idea of the west wind as a spirit, similar to the spirit that animates Shelley's speaker to want to scatter his writing all over the world. He writes: "Be thou, Spirit fierce, My spirit! Be thou me, impetuous one!"
The speaker understands the leaves that the west wind blows as a prophecy of new birth and life in spring. Likewise, Shelley, a radical, saw in his own leaves or writings a prophecy of a new world waiting to be born.