Answered question
I'm going on a trip and want to change my excess data from my plan (bonuses I have) into a travel add-on for the states. Is it something that can be done?
I don't think that can be done without changing your entire plan to Canada/US, which would only apply as of the next billing date.
Other answers
Sorry but is not possible.
When are you going to USA?
If it is after the current billing cycle, then you can modify your plan coverage to Canada & USA. All of your plan services will function in both Canada & USA for the duration of your next billing period.
You can revert back to original coverage the following billing period.