The decreased US production is the result of enviro-whackos and drought. Beef producers are getting a higher price for their cattle right now. I work at a cattle auction and have, off and on, for 30 years and I've been amazed at some of the prices.
The part about Canada is probably making a difference but in the beef industry diseases aren't taken lightly. Our state has a Tuberculosis quarantine and every cow has to test negative before it leaves the state. This is because ONE cow in a dairy herd tested positive and the quarantine will not be lifted for 7 years and only if there are no more positive tests.