I think you're letting your imagination run away with you.
First of all, I have never heard a Democrat or liberal say they would like to just ban all guns altogether. I hear this from Republicans all the time. I don't think it's either likely or possible!
After Sandy Hook 90% of Americans and 70% of NRA members wanted the gun show loophole closed. The Republicans HAD to oppose the measure and kill it, for their own political purposes. How did they justify this? "Obama wants to take all your guns away."
Secondly, it was the Republicans that wanted to change the US into a one-party state--Karl Rove's 'Permanent Republican Majority'. I agree with you, that would be a disaster no matter which party it was. BUT the two party system tends to be self-balancing. When one party gets ahead it eventually overreaches, and the other party takes over. We go back and forth. Some people think the GOP is in its death throes right now. I'm not so sure. But we all agree that if the GOP dies, another conservative party will spring up to take its place. The Democratic Party is pretty much the same party going back to Thomas Jefferson, but we've gone through several conservative parties-the Federalists, the Whigs, the Free-Soilers and Know-Nothings, and finally the GOP.
Finally the 'massive influx' of immigrants is enormously exaggerated. Nobody really knows how many there are (because they're UNREGISTERED!) But BOTH parties LOVE immigrants. The last president who gave them amnesty was Reagan! The last one who tried and failed was GW Bush. Immigration reform is just one more issue, like gun control, that the Republicans have handed Obama on a silver platter. When we have another Republican president, he will also try to do immigration reform!