The problem with the rule that you have now is that you are not doing it only for US purchasers. It will apply this rate regardless of the country selected. You will need to modify this rule if you want it to be for US only. You will need to add two more conditions. You will need to check that the session variable exists, then see if it set to US. The name of the session variable that you need to check is:
eCartCheckoutForm_shipping_country
This holds the shipping country selected by the user. You will need to check that it exists and it is set to US. For the international you would do almost the exact same conditions for the trigger except you would specify where this shipping country session variable is not equal to US.
You nearly have it correct now, you just need to add in these other checks, then you can repeat the process for your international rule.
