I wish that were true, but I suspect that the American people have become too passive to resist a dictator. He won't take over by force, but cloaked in legitimacy, just like Hitler and Mussolini did. Heck, you don't even have to go back that far. That's Putin's playbook, too. A Republican President also has a Supreme Court that favors very strong presidential powers and a permanently divided and largely impotent Congress. No real resistance there.
So, what's left? The police? American police would love having more power under a dictator. The public hates cops these days, and a dictator would restore their "rightful place" as respected and feared enforcers who will "clean up the streets".
The military? Well, that's a wild card. They may not support a dictator, but they also don't want to start a civil war. I think a US dictator will give himself enough legal cover and legitimacy to convince the military to hang back from interfering in politics.
The most likely source of resistance is from individual states. However, I'm not sure what they can do, realistically. Secession would certainly start a civil war, which would play right into the dictator's hands, giving him the perfect excuse to suspend rights and use the military for domestic purposes.