The key is the part I highlighted. Two of the pillars of the way the Founding Fathers set things up are local control and mobility. If the locals want to fund it, they can put forth a referendum to use local tax dollars (from sales tax, parking fines, whatever). If the measure passes, and a particular citizen doesn't like it, he can move.
When it is federal dollars, I - a non-resident of Bristol - have not had a say in how my tax money was spent, and it makes no difference if I get up and move or not; it is still being funded with federal monies.
Now, that said, I agree with you; improvements such as the one to the train station in Bristol should not be paid with public monies. I would vote against such a resolution.
I understand fully your logic, but what I'm saying is that geography shouldn't matter. Even in a single county, there will be a lot of people who are taxed for the thing and will never derive any benefit from it at all.
If the locals want to fund it,
The way these things work here is that some group who stand to benefit form a tax referendum (ie like a consortium of construction companies) will call themselves something like "Citizens for a better Bristol" and maybe spend $300,000 - $500,000 in an advertising blitz just before the election touting the advantages of whatever local pork/squander their accomplices in county government are setting up.
Since you can never go wrong underestimating the intelligence of the average voter, and it isn't feasible for those of us who want to keep our money in our pockets to mount a counter campaign - these things usually pass even though most people if they thought about it (or were at least capable of rational thought)would see that it was no benefit to them and a detriment to their pocketbook.