Upvote:13
Urban warfare is a complex and difficult form of warfare, very different from that portrayed in modern computer games like Call of Duty. There are very good reasons why the military (not just in the US) prefers not to fight in urban areas. As far back as the 6th century BC, Sun Tzu observed in his classic work The Art of War that
βthe worst policy is to attack cities. Attack cities only when there is no alternative.β
Of course, he was talking about walled cities, but the principle remains true today. The terrain in cities favours the defenders.
That said, you have named a number of significant urban battles in your question, although I wouldn't agree with your assessments of most of them. The Battle of Aachen, for example, was certainly not the walkover that you seem to think it was. Similarly, the fact that X Corps suffered over a thousand casualties during the Second Battle of Seoul indicates that US forces were far more involved in the battle than your question suggests.
Perhaps a good starting point might be for you to read Alec Wahlman's Storming the City: US Military Performance in Urban Warfare from World War II to Vietnam (2015). He focuses on four urban battles between World War II and Vietnam (Aachen (1944), Manila (1945), Seoul (1950), and Hue (1968)), and examines each battle in some detail. Of particular interest in Wahlman's book is the operational context of each of the battles (too many texts seem to describe battles as if they occurred in splendid isolation).