Poland is doable if you stay out of major cities. You can rent a studio for $300 (incl. all utilities). Food, if you cook, will cost you $200-$250 ($300-$400 if you don't cook and want to eat out only). Wired Internet and cell phone will be around $20. State-provided health insurance is about $120 per month (this is "socialized medicine", so it provides everything with no deducible, up to treating cancer etc.), but c…
Is car ownership pretty affordable overall? (Insurance, fees, etc)
Yes, very affordable. Yearly mandatory insurance, without any discounts for crash-free driving (as I doubt they'd honor insurance histories from foreign countries), is perhaps about $300. Mandatory yearly checkups are $30. Cars themselves are a bit pricier than in US - mostly due to VAT being higher than US's sales tax I guess. But, maintenance is way cheaper - there's plenty of cheap and skilled mechanics who will improvise fixes using scavenged second-hard parts (which they themselves will provide). Rebuilding an engine will cost you perhaps under $400 in labor, while I suspect it's in thousands of dollars in US.
Gas is currently $5.5 per gallon. Most people drive cars with low fuel consumption, so they're easy to get on second-hand market. Also, if one is particularly stingy about fuel costs, it's popular to own cars fueled by LPG. LPG is currently $2.5 per gallon.