I think most computers, laptops, and cell phones are equipped to go both ways from the start. Recently I brought a laptop and cell phone from TL back to the USA, and both are working fine with no problems. And most US electrical outlets accept both two-pronged and three-pronged plugs (but the two prongs have to be vertical, not round like the ones often found in some Malaysia, Thailand (and elsewhere) dwellings and offices..

I brought an electronic keyboard (piano/ organ) with me from the USA to Thailand, and the power cord "smoked out" immediately when we plugged it in at church. Fortunately, a local technician that there was a kind of "switch" inside that should have been turned to a different setting before plugging in, and the repair was quick and cheap.