Yes, but.
And the "but" is because that's exactly what happened with Bush. Since it happened so recently, it's less likely that it will happen again to the same degree. Representatives may be a little more recalcitrant and not follow the leader so easily, knowing how things turned out last time.
It's kind of a glass half-empty, glass half-full phenomenon. If someone's expecting Republicans to go Tea Party with Romney in the White House, they're going to be disappointed. As you say, that's not the way things happen. But if you compare a Romney presidency to how things were in the Bush years, you may be surprised that Congress does show a bit more backbone this time.
BTW, you are thinking you're making a great argument against Romney. For some people it will work the other way around. That is to say, for a some Republicans the idea that the party will circle the wagons for a Texan or blindly follow an evangelical but won't do the same for someone from the coasts or a Mormon is objectionable. I suspect that's why Ann Coulter and other East Coast conservatives embraced Romney with a closeness that conservatives from other parts of the country may find objectionable.
No offense, but that's just silly. As a native Californian who lived there at the time, I strongly supported George Bush in 2000, and would have supported him even if he were from Massachusetts.
I may love Texas, but a candidate's regional origin is completely irrelevant to me. It's their record of accomplishment and ideological grounding that either draws me to them, or repels me.
Case in point: Sarah Palin. The fact that she's from Alaska doesn't mean a hill of beans to me. It's her record and what she stands for, that has earned her my support.
Here's another: Rick Perry. Although he's the Governor of my state, and has presided over a long run of prosperity in this state, he's not really my kind of guy. I think he's far too moderate, and I don't trust him to make the conservative choice on every decision.
Then there's Mitt Romney. Now here's a man, who if you simply studied his record as Governor of Massachusetts, and didn't know who he was, you'd swear that he was a liberal Democrat. That's what his record shows. That's repulsive to me, and is a complete deal-breaker. I can't, and I won't vote for someone like that under any circumstances.
As to how a Republican dominated Congress is going to behave under a Romney administration, well, you'll see. They're going to roll over for him like trained pets. Too bad they won't be rolling over for any of the right reasons. I don't expect them to put up much of a fight when he begins rolling out his own Socialist agenda.