Guerilla warfare has been extremely effective against the US military for decades.
There are also a LOT of people still working within the government who do not support their current leadership. They can't ALL be replaced by loyalists, and with every replacement they get weaker, and the Resistance gains another experienced insider.
Resistance Guerillas don't all have to carry guns and be fighters. Those disgruntled federal employees are perfectly placed to cause all sorts of chaos, leaks, sabotage, weaponized incompetence, malicious compliance, etc. They will be as important to the fight as those willing to commit violence.
Thanks, I appreciate that. We already have brutal enemies within our own country, we don't need our neighbors hating us for the actions of those enemies. If America falls to the Maga Nazis, so will Canada. We have to band together to crush and purge them.