I have seen this post, and I wanted to offer a slightly different point of view as I have memberships in multiple US programmes in addition to my BA, LH, and AF European cards.
Our US friends have always been given other perks for their loyalty to the airline. For most of us European based travellers we cherish and expect access to lounges. I am not sure if our US friends do. What they expect however, are free upgrades. So, if you look at US programmes this tends to be the biggest perk – free domestic First class upgrades. Additionally, “System” upgrades are awarded allowing Gold/Platinum members free upgrades on several long-haul flights a year. Let me give you another example: when I was UA Premier Exec (Star Gold) I lived in Germany and travelled to Denver three times a year. It would cost me roughly the same in miles as I would earn on the round trip to upgrade via my IAD or ORD routing.
As our flights in Europe tend to be less than 2hrs, the upgrades may not seem to important. Now, think of NYC Area to Miami is 3hrs, then an upgrade is important.
Honestly, if free lounge access is what the US based travellers expected even with First ticket then I think it would have been done. There are some odd discrepancies however. By the looks of it; if you are on transcontinental flights from the NYC area airports to West coast airports like SFO, LAX, SEA you tend to get lounge access if you fly in Business or First. I know that UA and AA offer access to First lounges for those passengers.
So in conclusion: different perks provided in different markets. Simply put.