Best liquid investment for a US expat

I have a windfall which I'd like to invest, but due to market uncertainties plan to DCA over the next two years. What's the best thing to do with the cash in the meantime? As a US taxpayer I can't buy US bonds through a broker (and I believe there's a $10k limit anyway). I have an IBSJ account but it seems that unlike IBKR they don't even provide interest on cash, so my current situation is no different from stuffing it in my mattress.

by foof