You are visiting the US, you will leave and take your things with you.
That means that you do not 'import' the electronics, you 'temporary import' them.
This means that you look at different 'maximum allowed' level.
Basically, as long as the customs officer is convinced that you will take them with you when you leave, there is no hard maximum. The harder thing might be to take them back into your home country if they look new and valuable.
If you still have the sales bill, take it (or a good quality photo copy) so you can show the age and value and where you bought them. You do not need to pay tax bringing back things to the country you bought them.
If they are still rather new, valuable or you do not have proof of buying, you may want to get them registered as yours before you leave your home country. An ATA carnet is the way for that but might not be worth it for most used electronics.