Currently, the WORST airport in the USA is Detroit Metro (DTW). The concourses and alley-ways are very narrow, there are not enough gates, parking sucks, and airport access is always bottle-necked during peak periods. Connecting with NW flights at DTW is a nightmare! By far, it is thw worst major facility in the US that I have seen.
Fortunately, the county is now building a new mid field terminal with 76 new gates, an additional runway and new access roads. The new terminal is supposed to be "the best of the best" when completed next year. This expansion is years over due, since the airport is WAY over capacity. If any of you have been to the Northwest Terminal at DTW, you know how aweful it is. NW actually instructed their pilots to always point out the new mid field terminal to the passengers as they pass the construction while taxiing. They want to continually remind their costumers that they are fixing the problems. Interstingly, DTW is one of the fastest growing international gateways. NW alone flies non-stop to NRT, NGO, KIX, PEK, LGW, FRA, CDG, MXP, FCO and AMS. Alitalia will also begin daily flights to FCO in April.