After a lot of research, I finally came up with the biggest suburb in the United States. It is San Jose California. Here is a quote about San Jose, a suburb of neighboring San Francisco.
It will always be san francisco's ugly step-sister. it will always be in sf's shadow. san jose is nothing more than a joke of a town!!!!! ha ha"
Hahaha... you are right. SJ is nothing more than a giant suburb (even though this "suburb" has a larger population than the "city"). They don't have anything that resembles a real city, like skyscrapers, high rise apartments, vibrant financial district, etc.
Pictures of the San Jose skyline confirm that this city of 925,000 people (more than San Francisco) is nasty. This is all Overland Park will ever be at most. High populations don't make a city. KCMO is a real city. Hell lets compare the San Jose skyline to the San Francisco one.
Now here is the bigger city, San Jose.