OK, one, your intro is far too long, its the 3 reasons that should be longer, i dont care for grammar much, unless it makes it a reading problem, but the style of any persuasive essay is, as such:
Intro Paragraph:
Intro sentence, thesis sentence, 3 supporting reasons summarizied, transition sentence to next paragraph
1st Body Para:
First supporting reason, evidence/quotes from sources(at least 6 sentences long)
2nd body para:
Second supporting reason, evidence/quotes from sources(also at least 6 sentences in para)
3rd Body Para:
third supporting reason,evidence/quotes from sources(5 sentences)
Concluding Para:
Summarize your main points and restate your thesis if you want, and restate the purpose in an indirect manner(not 'this is my purpose in writing this ______').

Do this and one, your history teacher will probably give u and A, two your teacher will be very impressed with you as this is a basic AP World History Style essay, three, well i dont know what three is, probably something random will happen too.