The correct spelling is devastated, not devistated.
The first letter should be capitalized because of two reasons: 1. Pakistan is a proper noun. 2. The first letter of the first word of a sentence is capitalized.
This is a long, run-on sentence that lacks proper punctuation. The clauses are misplaced as well. The correct sentence should be "After enduring multiple invasions by other countries in 1956, the country gained independence from the colonial ruler, Britain. OR The country gained independence from the colonial ruler, Britain, after which it endured multiple invasions by other countries in 1956.
The correct sentence should be, "Unfortunately, the floods generated by monsoons, have wiped out much of the country's infrastructure, including bridges, electrical plants, transmission wires, hospitals, schools, and roads.
The correct sentence should be, "Many were forced to flee with just the clothes on their backs."
6,7 and 8 can be combined into one sentence. Other countries are sending food, medicine and building supplies for help.
"Roosevelt's speech was a big success because he was able to calm the American people in just a time of panic. ... This speech showed the American people that they weren't alone at a time like this, that they had someone who understood what was going on and what they were going through."
