Federal funding mostly comes from the states with the highest economic activity. Unless you're disputing that states with higher number of individuals and economic activity doesn't correlate with more taxes paid to the federal government.

And on the iowa website itself [1] I can see the grants and federal funding used by the state government. My point being that if the more rural cities were required to pay for everything themselves, they would not be able to.

[1] https://iowadot.gov/transit/funding-programs-and-application...