”The Lord himself affirms that Baptism is necessary for salvation. He also commands his disciples to proclaim the Gospel to all nations and to baptize them. Baptism is necessary for salvation for those to whom the Gospel has been proclaimed and who have had the possibility of asking for this sacrament. The Church does not know of any means other than Baptism that assures entry into eternal beatitude; this is why she takes care not to neglect the mission she has received from the Lord to see that all who can be baptized are "reborn of water and the Spirit." God has bound salvation to the sacrament of Baptism, but he himself is not bound by his sacraments.” CCC 1257
However there is a “loophole” for some to be saved without Baptism:
”Since Christ died for the salvation of all, those can be saved without Baptism who die for the faith (Baptism of blood). Catechumens and all those who, even without knowing Christ and the Church, still (under the impulse of grace) sincerely seek God and strive to do his will can also be saved without Baptism (Baptism of desire). The Church in her liturgy entrusts children who die without Baptism to the mercy of God.” Compendium of the CCC, #262
But what about Protestants baptized in their own faith (according to the RCC)?
” Baptism constitutes the foundation of communion among all Christians, including those who are not yet in full communion with the Catholic Church: "For men who believe in Christ and have been properly baptized are put in some, though imperfect, communion with the Catholic Church. Justified by faith in Baptism, [they] are incorporated into Christ; they therefore have a right to be called Christians, and with good reason are accepted as brothers by the children of the Catholic Church." "Baptism therefore constitutes the sacramental bond of unity existing among all who through it are reborn." CCC 1271
The only sticking point here is the “properly baptized”. For the “sacrament” to be valid it must be done in the correct manner:
Baptism, the gateway to the sacraments and necessary for salvation by actual reception or at least by desire, is validly conferred only by a washing of true water with the proper form of words. Through baptism men and women are freed from sin, are reborn as children of God, and, configured to Christ by an indelible character, are incorporated into the Church. Code of Canon Law 849
” For a sacrament to be valid, three things have to be present: the correct form, the correct matter, and the correct intention. With baptism, the correct intention is to do what the Church does, the correct matter is water, and the correct form is the baptizing "in the name of the Father and of the Son and of the Holy Spirit" (Matt. 28:19).
Unfortunately, not all religious organizations use this form. In fact, Jehovah’s Witnesses sometimes use no formula at all in their baptisms, and an even larger group, the "Jesus Only" Pentecostals, baptize "in the name of Jesus." As a result, the baptisms of these groups are invalid; thus, they are not Christian, but pseudo-Christian.” Excerpt from Catholic.com
” It is a valid baptism that makes a person a Christian. If a person is baptized validly with the proper matter (water), proper formula ("In the name of the Father, and of the Son, and of the Holy Spirit"), and proper intention (to baptize), he is ontologically Christian; that is, his very being is Christian. If he believes in the divinity of Christ and in the Trinity, he is theologically Christian—he holds Christian beliefs.
But as baptism imparts a permanent supernatural character upon the soul, a person’s status as a Christian is not dependent on how well he either understands or practices his faith.
Oneness Pentecostals are considered to be non-Christians primarily because they do not have a valid baptism: They baptize in the name of Jesus only. Ontologically speaking, they are not Christians because they do not have a valid baptism. Theologically speaking, they deny the Trinity and thus do not hold to classical Christian orthodoxy.
Most non-Catholic Christians who deny the Real Presence of Christ in the Eucharist (e.g., Baptists, Seventh-day Adventists) have valid baptisms. They are ontologically Christian. If they believe in the divinity of Christ and in the Trinity, then they are also theologically Christian.” Excerpt from Catholic.com
But yet even where “valid” Baptisms exist, the views of what Baptism accomplishes are quite different for Catholics and Protestants as Catholic.com outlines (of course I disagree with their conclusions):
“Catholics and Protestants agree that to be saved, you have to be born again… When a Catholic says that he has been "born again," he refers to the transformation that God’s grace accomplished in him during baptism. Evangelical Protestants typically mean something quite different when they talk about being "born again."
… many Protestants have abandoned this biblical teaching [baptismal regeneration], substituting man-made theories on regeneration. There are two main views held by those who deny the scriptural teaching that one is born again through baptism: the "Evangelical" view, common among Baptists, and the "Calvinist" view, common among Presbyterians.
Evangelicals claim that one is born again at the first moment of faith in Christ. According to this theory, faith in Christ produces regeneration. The Calvinist position is the reverse: Regeneration precedes and produces faith in Christ. Calvinists (some of whom also call themselves Evangelicals) suppose that God "secretly" regenerates people, without their being aware of it, and this causes them to place their faith in Christ.
… The anti-baptismal regeneration position is indefensible. It has no biblical basis whatsoever. So the answer to the question, "Are Catholics born again?" is yes! Since all Catholics have been baptized, all Catholics have been born again. Catholics should ask Protestants, "Are you born again—the way the Bible understands that concept?" If the Evangelical has not been properly water baptized, he has not been born again "the Bible way," regardless of what he may think.” Excerpt from Catholic.com
Overall I see two main differences between the RCC and the Protestant/Bible-only teachings on Baptism. First, the RCC teaches that Baptism is a “normative” necessity for salvation while most Protestants do not (salvation by faith alone). Second, most Protestants would not consider that Baptism makes someone a “Christian” (or born again). To be a Christian would require true faith in Jesus Christ – certainly not something that can be found in a baptized infant