It does prevent these uses, however, unless the content provider explicitly provides it. The US law says that the content provider does not need to explicitly allow it; it's a right granted to the user by copyright law.

Cool, can you show me how to play the content on my portable MP4 player please.

Unfortunately, no. I think you may be getting tripped up by the phrase "effective technological measures" - being "effective" is a very, very low bar. To quote s296ZF of the Copyright, Designs and Patents Act 1988:[0]

“technological measures” are any technology, device or component which is designed, in the normal course of its operation, to protect a copyright work other than a computer program.

(2)Such measures are “effective” if the use of the work is controlled by the copyright owner through—

(a)an access control or protection process such as encryption, scrambling or other transformation of the work, or

(b)a copy control mechanism,

which achieves the intended protection.

[0] http://www.legislation.gov.uk/ukpga/1988/48/section/296ZF