I am not a lawyer... that being said:
I have read reports about e-bike legal hassles on other forums. From their experience (including court appearances) the law quoted does not preempt state vehicle codes, but preempts safety equipment regulations.
For instance, the vehicle code can still require registration, licensing and insurance for an e-bicycle, categorizing it as a motorized bicycle (moped). The state law cannot require an e-bicycle be fitted with turn signals, lights (except for night operation), or functioning horn.
This interpretation may be completely wrong, but that is the user experience I have heard.
Some states have incorporated an e-bike exemption/equivalence into their vehicle codes, usually following the 750W/20mph limits outlined in the federal law. Some states still insist the e-bikes are not bicycles and require special registration and licensing. I believe Michigan is one such state (
http://www.michigan.gov/documents/msp/TSS_Field_Update_26_180953_7.pdf).
If in doubt, check out your state's vehicle code, the FAQ's from the state's Motor Vehicle Department, or consult with a traffic lawyer. Otherwise, keep the bike stealthy, and don't do stupid stuff that will draw the attention of the local traffic enforcement folks. Most of the time you will be fine. If nothing else, keep a copy of the quoted legislation with you. If some cop decides to cite you as being in violation of the state's vehicle code you can politely discuss with him the implications of the law and suggest he needs to do further research before handing you a citation.
Fortunately, I live in California, where they have adopted e-bike legislation into the vehicle code that is even more generous than the regulation you quoted. According to the California Vehicle Code, anything with less than 1000W / 30mph is a "bicycle" and must be regarded as such. The only exception is a minimum rider age of 16 and a bicycle helmet mandate that applies to all riders, not just minors.