So is the Vcc (5v) pin on devices that are running the ATmega32u4 controller, such as the Arduino Leonardo, Micro, and Teensy 2.0, capable of drawing the full 500 ma of a USB 2.0? Or is the Vcc pin power regulated by the controller beforehand, therefore, limited to the 40ma maximum on an I/O pin? I wanted to make sure before I accidentally blew out a controller.
The Atmega32U4 has two Vcc pins each capable of drawing 200mA Absolute Max, so 400mA max.
There is no regulation outside the 500mA PTC Resettable fuse on the USB line on Arduino boards - I haven't looked at all schematics to see if all the boards you listed have that.
If your circuit allows more than 40mA, the IO pin will try to support that up to the point that the IO output transistor(s) blow.
This is another "XY Problem".
You do not go about calculating maximum currents in relation to the USB supply - that has nothing to do with it.
You simply make sure that no device you connect to any I/O pin can possibly draw more than 25 mA at the very most - that figure is 25 mA, not 40 mA - and you do so by providing series resistors for LEDs or ensuring that no other device (or combination thereof) connected has a resistance less than 200 Ohms.
You also calculate to respect the totals for I/O pin groups that CrossRoads cites.
That is how you do it.
My intention was not to make the IO pin the subject of the matter. I was not clear about that. I only wanted to know if it was safe to connect around 80 LEDs, running around 2-3 mA, directly to the Vcc pins. Which I now know the answer to. Thanks guys!