Most of what you say is probably true, but the fact remains that most Hispanics and now most Asians prefer the Democrats.
The true story here is that Romney is getting 60% of the white vote, yet he is only a few points ahead. As recently as the 90s, winning 60% of the white vote would equal a landslide, easy victory. But it doesn’t now because the GOP has been too stupid and and too cowardly to stop mass immigration (legal and illegal). Mass immigration was always going to favor the Democrats. It’s obvious really. The GOP should have ended it decades ago before it really go out of hand. Instead they’ve made it worse by passing absurd expansions of immigration like the ridiculous Diversity Visa Lottery.
The writing is on the wall. As someone else has said; either the GOP will end mass immigration, or mass immigration will end the GOP.