I certainly wouldn't presume or preach to others with regards to how they view their country, however:
1. We (I'm an expat as well) pay little taxes to the U.S. because of the foreign earned income credit. The paperwork is onerous, yes. But it's not as bad as some make it out to be, unless you're in an exceptional income bracket.
2. A U.S. passport is a powerful thing. And as the OP mentioned, the benefits are real. We look after our own. http://www.passportindex.org/byRank.php
3. Many U.S. expats wouldn't dream of renouncing their citizenship, because it simply means more to them than that.
It's more than residency, it's identity. And it's something we pay into. Many Americans will tell you...they don't like a lot of taxes...but they /will/ pay taxes, and they expect everyone to. It's a "we're all in this together" bit. Even if you're abroad, and you're paying a paltry amount, you're still chipping in.
Just something many of us do.
This is the part that often (note: not always) leads to valuing an American higher than a non-American. I have real problems with that. 911 is virtually celebrated, while larger tragedies the world over are not. What makes an American soldier's life more worthwhile than a baby born with Aids in some African backwater? If you believe all the flag-waving, nationalism. Otherwise media.
And I get that small number of deaths is a tragedy, a large number is a statistic. That doesn't change the reality - a life is valuable no matter who's it is, and where that person lives.
I'm a citizen of the world. I was born in Africa, have lived in the US, and now live in Europe. I rate myself as no better or worse than anyone else on this planet, including Americans. Most of all I'm insanely grateful to not be American.
AFAICT most of the money isn't spent here, it's parked here as a hedge in case something goes south in the home country, usually in real estate holdings. The biggest effect I can see is that housing in the city is too expensive for the locals now so families are being driven out into rural areas.
It's not like federal income is an admission fee. Or a direct tax on something the citizen uses (like a toll road). You benefit just as much from the government building a VA hospital, AIDS research, or a US carrier stationed near Syria.
You don't suddenly stop being an American when you go live somewhere else.