There is no single data point on this that I know of. Each agency of each government (state, local, federal) tracks their own spending on language services. They are only tracked together for specific reports.
According to the OMB Report to Congress in 2002, the US spend 1.9 million a year on written translations for food stamp programs alone. Oral translations for food stamps programs was another 21 million a year.
Multilingual outpatient services (legally required) cost the industry 180 million.
Expenses like these are scattered all over the economy.
But also bear in mind, that realistically, some portion (probably small) of these costs are offset by creating jobs like translators, language teachers, etc.