People keep talking about the "subsidies" as if they apply to all suburbs. It seems to be an article of faith. It really needs some evidence (preferably from an unbiased source).
There are probably exceptions, of course, but surely the basics are not controversial, e.g. that public infrastructure spending per capita tends to be much higher in suburbs than in urban areas, carbon emissions per capita are much higher in suburbs, etc. Not to mention that political representation in the United States favors lower density areas.