I'm interested in the birth and growth of nationalism in Early Modern English to the present day. Are there any good speeches, pamphlets, or general works which reflect the growing use of national identities to support foreign engagements or other conflicts?
I don't know of any works specific to your areas of interest, but Imagined Communities: Reflections on the Origin and Spread of Nationalism by Benedict Anderson is a foundational text in the study of nationalism. Read that first if you haven't already, then branch out. It's a fabulous book.