 Tear down this wall!  was the challenge issued by United States President Ronald Reagan to Soviet Union leader Mikhail Gorbachev to destroy the Berlin Wall, in a speech at the Brandenburg Gate near the Berlin Wall on June 12, 1987, commemorating the 750th anniversary of Berlin.n the 1963  Ich bin ein Berliner  speech, U.S. President John F. Kennedy stated the support of the United States for democratic West Germany shortly after the Soviet-supported Communist state of East Germany erected the Berlin Wall as a barrier to prevent movement from East to West.
Feedback happens when a microphone picks up sound from speakers and then pipes that same sound back through the speakers and picks it up again. The never-ending loop of ear-pain is frustrating to experience, but fairly easy to fix by adjusting the levels of the speakers and microphone.
Yes, cheap power supplies can also cause part of the problem, because they aren't shielded properly. Popping that only happens when turning the speakers on or off, though annoying, is common and I don't worry about it. You could also try cutting off the grounding prong/or adapting it so it goes away. The ground is often a source of feedback for speakers, an adapter would be like 99c at any hardware store.