Does the power strip do anything beyond read the +5V a connected USB port provides? (Do you see anything in
dmesg when you attach it? Does the output of
lsusb change after you plug it in?) If not, the kernel may not even recognize that anything is attached. You can't tell a device to suspend if it never enumerates itself: it would never show up under /sys/bus/usb/devices, and with USB you suspend devices, not ports.
This file contains one of two words: "on" or "auto".
You can write those words to the file to change the
"on" means that the device should be resumed and
autosuspend is not allowed. (Of course, system
suspends are still allowed.)
"auto" is the normal state in which the kernel is
allowed to autosuspend and autoresume the device.
(In kernels up to 2.6.32, you could also specify
"suspend", meaning that the device should remain
suspended and autoresume was not allowed. This
setting is no longer supported.)
So according to that last little statement, if you have a kernel newer than 2.6.32 it sounds like you cannot force a USB device to suspend anyway.
Sorry that I can't give you the answer you actually wanted, what you were trying to do sounds pretty neat, but I hope it was helpful.