It's not just an American thing, Nautilus. Consider a pretty standard DSLR system: Nauticam NA-5D3 housing, a dome port for your fisheye, and a macro port, plus two Sea & Sea YS-D1 strobes, plus cables, arms, clamps, floats, plus strobe batteries, chargers, etc. That will just about fit perfectly into a Pelican 1610 and it will weigh right around 50lbs - right on the limit. From that basic kit, what could possibly be eliminated to make the box lighter? The box itself weighs around 22lbs, so you'd think that would be a great place to save some weight. But how do you keep the airlines and airports, who couldn't care less about your belongings from damaging your equipment?
When it comes to carry-ons, as I said earlier in this thread, just a pair of 5DMK3 bodies, a 8-15, 16-35 and 100mm macro plus chargers and batteries will be over the limit at the gate. And then there's your computer. Let's face it, if you're serious about underwater photography, it's madness not to bring a laptop, since otherwise you have no way of identifying problems with lenses, sensors, etc., unless you can closely inspect the photos in the field. So you have your 13" Macbook Pro, and a couple of 2TB Thunderbolt drives, plus chargers, etc. And once again, that bag alone is overweight.
I don't know how anyone doing serious underwater photography can reduce weight, regardless of their nationality. I approach this whole travel thing as a war. It's you against the airline and airport authority. No one cares about you or your things. You just have to get in there and push push push your way through. Use every tactic and strategy you can, because you are powerless against your airline. Honestly, it's you against them.
This may sound overly simplistic, but perhaps some careful thought as to what you really need to take on the trip may be the answer.
I travel a few times a year to various tropical destinations taking dive gear and a 4/3 camera rig with strobes. (I know that's an immediate advantage over DSLR travellers)
Even so, after a while I realised I was repeatedly taking stuff I never used! I can now pack everything I need in a lightweight check-in roller bag (23kg), a carry-on backpack (7kg) and my one personal item (my camera and two lenses in a small camera shoulder bag) that I can carry on. Up to now I have resisted taking a laptop, using a smart phone instead, but I think that may change soon!
If it looks like I may be getting close to the baggage limit of 23kg (Australian airlines) I buy an extra couple of kg in advance of travel which is a lot less expensive than paying excess baggage at the airport.
Now without wishing to be too controversial maybe this baggage issue is an American thing! I am amazed how much stuff people think they need to take and this was driven home when I went camping with a couple of American friends a while ago. Wow! everything including the kitchen sink!
Perhaps having such generous domestic baggage allowances in the USA makes it more difficult to be a bit ruthless when packing for an overseas trip?