Unless you're Merion, Shinny or one of the other upper-echelon East Coast clubs that the USGA is enamored with, you need, in a word, EVERYTHING. You need length. You need difficulty. You need a good tree management program. You need a site with room for a bunch of corporate hospitality. You need cooperation with municipalities that would get involved in transportation, traffic and security issues. You need a cooperative membership. You need to be willing to let them (through an approved architect) tell you that your golf course needs to change X number of greens, remove XXX number of trees, expand your practice facility and just about anything else that you need to accommodate the event.
If you're Merion (just as an example), you don't need to do much of the above, because, well, you're MERION, for Chrissakes.