Here's the deal. We pay taxes and the government gives some of that money back to the communities that paid it. (The rest they use to pay for essentials like national defence and interest on the national debt or piss away on the federal bureaucracy and congress.)
They do not give it back in proportion to the tax payers in a community or in proportion to the amount of tax paid by a community - that would just build pockets of rich getting richer and poor getting poorer, They give it back in proportion to the number of people who live there and use the federal, state and local government services (roads, police, parks, libraries etc.)
If we use the $400 billion cited above, Every person counted (legal or illegal) means about $1333 per person - or $13,330 between now and the next census - to the state and local government. Since we will pay this money in taxes anyway, it is in our own best interest to ensure that every possible person in our community is counted so that the maximum amount comes back to our community.
PS: Hispanic background Americans are about 15% of the population. German background Americans are about 17%. Why is there no question about Germanic background? .... They have no lobby