It's a sort of 'yes and no' answer to this question. When the BBC, for example, signs agreements with programme makers, these agreements only permit transmission within the UK. For this reason, the BBC isn't allowed to stream most of its TV content onto the internet.
The same rules apply to other broadvasters throughout the world, so there's not that much TV content available. That doesn't mean, however, that its non-existent. See here:
http://wwitv.com/
(You'll definitely need broadband. Don't expect wonderful quality either).
Chris