It's not a cathedral, per se, just a parish church, but a personal favorite of mine; what I like isn't so much the architecture as the art - Old St Pat's in Chicago.

This really doesn't do it justice, but here's a link.

http://www.oldstpats.org/about/tour/index.html

More pictures here (among other Chi. churches)

http://chicagochurches.blogspot.com/