You won't be able to get to the USA to visit your sister; but you may be able to visit Canada or Mexico and meet there. This is easier for several reasons:
- Canada and Mexico do not have a visa ban for Syrian nationals;
- In Canada and Mexico you would not be visiting someone who already lives there; remember you have to convince the visa officer that you are not intending to immigrate. It will be easier to convince the officer thereof if you're not visiting your family at their home;
- Possibly, Canadian or Mexican border control is less strict in general (I'm not sure if this is true).
A friend of mine (UK citizen) meets their spouse (US citizen) typically in Ireland, because if they were to meet in the UK or the US it would be harder to convince the officer they're not intending to permanently stay with their spouse.