So sure the sun isn't helping but, if you were to "enclose" an additional part even beyond your attic and roof. That would help a whole lot more, But it would cost a GREAT deal. Also if you just used a reflective "paint"(if thats even legal) that would shield a good amount of sun too.

DC ventilating fans run by a solar panel and battery. I just added a ridge vent along the peak of my roof and this summer I will tear open the gables and build two large vents with DC fans that run slow and quiet. Thermostat controlled and much larger than the tiny all in one solar vents you can buy. On the cool shady side of the house the fan will draw air in and the other end will exhaust.

White roof. I just reshingled my roof with white shingles. They are supposed to reflect about 35% of the light. I am looking into elastomeric roof coatings that can reflect up to 85% of the light. The paint is for resurfacing older roofs but I plan to do it to my new roof. It's very simple and it works. In the sunbelt, white is the new green for roofs.

Other things I have done,

Sycamore trees to shade the house, they grow fast, have big leaves and lose their leaves for the winter after the heat is gone.

Insulation and caulk to keep conditioned air in.

Solar film on the windows. This reflects light but what I didn't know was the glass absorbs a LOT of heat due to the film. On a hot day you can touch the glass and it is HOT. So...

I added awnings above the windows for 2 reasons. It keeps the rain away so I can leave windows open more and it also keeps the sun off the glass. These awnings I made myself and it was a really simple and strong design, and cheap. I can do a tutorial if anyone is interested.

Another good idea is to replace window screens with solar (sun blocking) screens that cover the whole window, not just the part that opens.

Last, I plan to experiment with spraying water on the roof. Also, you can now get tiny little misting nozzels in the irrigation dept at home depot. These are often used to cool the air in outdoor restaurants and cafe's and are really neat.

 If you have cooling problems during the summer you likely have heating issues also.

 I'm studying to be a Home Inspector when i retire.Passed the internet test so far LOL

What I actually tried is, I installed a small $70 thermostat-run attic fan that pulled air from inside the attic out the vent screen at one end of the attic. It used the amount of electricity that an incandescent bulb would use, and cut my AC bill from $160 to $80 (in the summer). I installed it with a switch so I could de-power it 7 months a year.

Once, while I was in the attic, I learned a little about fluid air flow characteristics. The fan was on one end of the attic, and it drew air in from the soffet vents located around the entire edge of the attic, so only half the attic air was cool. By sheer dumb luck it was the half over the house, and not over the garage. If I had stayed, I would've added a second fan on the other end.

These attic evacuation fans can be run while the AC is running inside the house, thats why I chose it first instead of the whole house fan (which I may have added later).

Any windows that get hot, shade them on the outside (instead of just blinds or shutters inside). I honestly feel I got a good result for about 5 months a year by stapling loose weave cloth onto the eaves of the entire south wall, it hung down 3/4ths to the ground, and shaded the wall and windows. The cloth was stored in the garage the other 7 months.

As you noticed there are many things you can do. Some more cost effective than others.
Check out the options, consider your situation and skills to determine what works for you.
Many good suggestions already made so will not repeat many of them.

Vent the attic with sufficient air, the goal is to keep as close to outside temp as possible.
Even with good venting the HOT roof radiates heat down to the house.
Reflective radiant films above the insulation is more or as effective as a second roof with ventilation.
Wind induced ventilation can do a great job without requiring power, even with low winds.
A cool attic is more cost effective then more insulation.

Whole house fans are effective only if the evening air temperature drops low enough to make use of it.
If the evening air temperature is low enough then store the "cool" in a thermo mass, maybe eliminating AC run time.

Fans
Fan power is a cubic function, twice the air flow 8 times the power. Air foil shaped blades improve air flow 26% or more, in cubic functions this is half the power. Ceiling fans, air blowers, while house fans use less power with air foil blades. Slow moving air for a long time will use less total power than a high speed fan running for a short time.

Ground Water cooling, if your ground source water is below 60 deg then use it to cool house not AC. Discharge water can be used for watering the lawn or to fill a pond.

ICE block cooling, freeze a large block of ICE in the winter, use to cool Fridge and AC for house.
My home in MI needs 15 foot cube of ICE. Bury it in the ground.

Keep sun off AC condenser.
Keep sun out of home.
Consider pure water misting on AC condenser.
Desiccant to reduce humidity, assuming 60% humidity half the energy to cool is the latent heat of condensing the humidity out. Use AC condenser heat to dry desiccant.

Ground source heat pump.

As mentioned www.builditsolar.com has many inexpensive cooling ideas.