Specific investment advice is off-topic, but here’s some things to consider based on your question:
With the Treasury bond interest rate going up, we’re interested in getting some of these.
If you think the rate is going up in the future, then it would be better to wait until it does go up. Otherwise you’d be locked in to a lower rate and the value of your bond (if you were to sell it) would go down.
I would be paying possibly US and Canadian taxes on the earned interest
You would not be double taxed. Depending on your overall tax status, you would pay tax in the interest income to either the US or Canada, and be given a credit from the other for taxes paid.
US Treasury bonds are effectively risk free in terms of default. The US will almost certainly not default on its bonds since it can borrow and/or print more money to pay them off. It may lead to rough economic conditions in the future, but if you buy a bond you are essentially saying you’re satisfied with the rate of return that you’ll get over the life of the bond.
If you are buying it as an investment that you will sell later to make a profit more than just the coupon rate (which you can’t do for bonds you buy on TreasuryDirect, but you can if you buy a bond from a broker, for example), you’re essentially betting that interest rates would go down in the future and your higher-coupon bond will be more valuable.
