When Jig suggests that "we can have everything"? she is actually implying that, in fact, they cannot have everything and that the American is ignoring the fact that they must make difficult decisions. Jig is facing the choice of having a baby or having an abortion. If she has the illegal and dangerous abortion, she cannot have the baby. If she has the baby, she cannot continue the free and irresponsible life of travelling around Europe that she is currently enjoying. Moreover, if ‘everything’ includes marriage, the American isn’t even offering that option. Thus the comment highlights the difference between everything the American wants and everything Jig wants.
the reason jig says we can have everything very sarcastically is because, the american doesnt take note of the fact that she wants the baby and if she goes a head with the abortion which is what the american wants, she is not really having everything because what she really wants is to have the child, according to the american "everything" is the travelling, the drinking and the experience, and if the baby is born they wouldnt have any of it and they would have to settle down in life, so he uses those facts to manipulate jig into having abortion, so that their eventful life wouldnt stop