Generally you will not win a chargeback if the airline either gets you from Point A to Point B (regardless of whether you care for the city through which it routes you) or it refunds you for the fare because you chose not to accept the reroute. If those options are presented to you, youy will not prevail, almost certainly because you won't have a basis for a chargeback since you have to show you tried to work with the merchant first for one of those two options.

You must be aware, but just in case, you can claim original routing credit (ORC) typically, when you are routed on a different airline in these circumstances. I have been routed on UA when my AA flight was delayed 20 hours. I requested it. After the flight, I called AA and ORC was assigned at exactly the same mileage and LPs as if I had flown on AA. (This also applies when you are routed through different cities.)