High side switching can't be done with n-channel MOSFETs - your circuit is a source-follower which drop some volts (depending on the MOSFETs in question and the current drawn), and dissipate significant power. The MOSFETs are not really switches in this configuration, they are current amplifiers (with vast gain). In particular when running from the USB 5V the output cannot be anything like 5V, which presumably was the point.
Do high-side switching with P-channel MOSFETs, or low-side switching with N-channel MOSFETs (low side switching is problematical as there is no common ground between the supply and the load).