This question turns up quite often.
Instead of msn messenger...use yahoo messenger. It is the best webcam "chat" prog around (in my opinion). Easy to use, as reliable as chat progs get, etc.
And if you both have microphones you can talk and view each other at the same time. Which is nice.
Go to click here (I think) or search for it in a search engine.
Download the software, install it, make a username and password.....and away you go webcam chatting to your US relatives.
Yahoo have a help section on the web too...just in case you get stuck setting it up. But it really is quite easy.