Here is what the Catholic Church actually condemns in Jansenism;
•Some of God's commandments are impossible to just men who wish and strive (to keep them) considering the powers they actually have, the grace by which these precepts may become possible is also wanting;
•In the state of fallen nature no one ever resists interior grace;
•To merit, or demerit, in the state of fallen nature we must be free from all external constraint, but not from interior necessity,
•The Semipelagians admitted the necessity of interior preventing grace for all acts, even for the beginning of faith; but they fell into heresy in pretending that this grace is such that man may either follow or resist it;
•To say that Christ died or shed His blood for all men, is Semipelagianism.
These five propositions were rejected as heretical, the first four absolutely, the fifth if understood in the sense that Christ died only for the predestined. All are implicitly contained in the second, and through it, all are connected with the above-mentioned erroneous conception of the state of innocence and the original fall. If it be true that fallen man never resists interior grace (second proposition), it follows that a just man who violates a commandment of God did not have the grace to observe it. That he therefore transgresses it through inability to fulfil it (first proposition). If, however, he has sinned and thus demerited, it is clear that, to demerit, the liberty of indifference is not requisite, and what is said of demerit must also be said of its correlative, merit (third proposition). On the other hand, if grace is often wanting to the just, since they fall, it is wanting still more to sinners; it is therefore impossible to maintain that the death of Jesus Christ assured to every man the graces necessary for salvation (fifth proposition). If this be so, the Semipelagians were in error in admitting the universal distribution of a grace which may be resisted (fourth proposition).
http://www.newadvent.org/cathen/08285a.htm