If Canada was no country but a territory where people were denied the right to have a state to live in, and if they were launching rockets at the US, I think the US would colonize Toronto and declare the city part of the US. Wait no, I don't.
"If Canada was no country but a territory where people were denied the right to have a state to live in,"
To make it even more alike the situation, then, we should say if these were people living in Seattle who are illegal aliens from Central America living there because they were kicked out of their refugee camps in Mexico...
"and if they were launching rockets at the US"
Let's say from Seattle at Redmond instead, with restricted access points from Seattle because occasionally they keep trying to destroy Redmond.
"I think the US would colonize Toronto and declare the city part of the US. Wait no, I don't."
And instead of the US as we know it, let's say the US is just the I-5 corridor from Portland, OR, to Everett, WA. And let's transplant all that area into, say, the neighborhood of Nicaragua or Panama. And let's say all the surrounding countries have declared that the people who live around Redmond must be pushed into the sea. They don't want the people in Seattle who used to live in their countries to move back into their countries; no, they want to help them destroy all the Americans.
What would happen? Redmond would launch the Surface.
Can they control what goes through those borders? Can they control what happens in the airspace above their territory? Do they have a seat at the UN?
The answer is no to all 3.
Question: if I want to fly into Gaza, whose permission do I need? Hamas' permission is clearly insufficient: the IDF will shoot down any plane landing there. So they're not at all an independent state.
Being under embargo/blockade is not the same as having no state. When the US did the same to Cuba 50 years ago, Cuba didn't magically disappear or become invalid.
Do you know why the US did that to Cuba? They were smuggling missiles in. See a pattern there?
If you have no control of what enters or leaves your territory, no control over the air above your head or the electromagnetic spectrum, and no international passports, I don't see how you can be a state.
The whole point of a state is that it has some effective control.