Are you referring to WWI or WWII? For WWI, it was due to a complex system of alliances and a push from elected officials at home to get involved. If you're talking about WWII, it was because the Japanese bombed Pearl Harbor.
Answer:
because they were both fighting against the Nazis in Germany
Answer: Roman precinct walls
Explanation: The Great Mosque of Damascus was built by the Umayyad Caliph Al Walid. The Caliph selected a site that had previously been a temple, first to Hadad and then Jupiter Dolichhenus. The temple had a Roman design and when Al Walid demolished the temple, he left the Roman Precinct walls which gives it its distinct Greco-Roman architecture look. The walls formed the entry to the mosque and are still present in the mosque.