Oftentimes, either when I read Roman Catholic apologetics or I interact with Roman Catholics, I notice that there is a recurrence of an assumption, and that assumption is actually, when one gets right down to it, a logical fallacy. Permit me to explain...
In the world of logical fallacies, there is a particular fallacy known as a false dichotomy, also known as a false dilemma. This belief teaches that there are a limited number of options (most popularly two), when in fact more options exist or can exist. For example, it would be a false dichotomy to say "In American politics, you're either a Republican or you're a Democrat" when a person could also be a member of a major third party, such as the Libertarians.
It should be quickly noted that there are indeed times when the options are limited, and in such a case a false dichotomy does not automatically exist. For example, if you go to a restaurant and the waiter asks "Soup or salad?", you can't immediately say "That's a false dichotomy!" simply because there are two options - the restaurant does indeed only have two options there.
However, in the case of churches and forms of what calls itself Christianity worldwide, many within the realm of Roman Catholic apologetics appear to believe that there are either two options: Roman Catholicism (or at the very least, loyalty to the Roman bishop) or one of the Protestant sects. This is a false dichotomy because this is not the only option available. In addition to Roman Catholicism, one can likewise choose Eastern Orthodoxy, the Coptic Church, or even the Church of the East (traditionally labeled "Nestorians" although they have denied believing in the historical definition). This is but a sample of other groups who make similar claims as the Roman Catholic Church, such as apostolic succession or a form of holy tradition. If one wants to go to the "church of the apostles," then, certainly on a surface level, there are a number of churches to choose from.
Now, I am not writing this post to necessarily support one side over and against another, however this factor is something that often gets ignored in Roman Catholic/Protestant dialogues, especially since the Roman Catholic side often attempts to woo the Protestant side towards a single church. This often happens under the rationale of the false dichotomy mentioned in this post - in fact, oftentimes it appears as if the Roman Catholic apologist is either completely unaware of the other "apostolic" churches, or is intentionally avoiding them. This especially comes out when said other churches are brought into the equation, and the responses I have encountered vary, depending on the maturity of the individual Roman Catholic: some ultimately stumble, because all the prize arguments ("we're the church of the apostles," "we're the church founded by God," etc.) suddenly come under scrutiny and there is no other defense; some attempt to shrug it off or be dismissive, which, when pressed with the differences between the churches, causes them to likewise stumble; some will try to find similarities between the churches to minimize the differences (for example, comparing Purgatory to Aerial Toll Houses), not realizing that these similarities are superficial at best and, when reviewing the worldview of the two churches, prove to be completely incompatible; those who are intellectually honest will have to confess that those churches likewise are in error, and will then have to defend themselves over and against the other "apostolic" options.
In the end, Protestants can probably take joy in the thoughts of someone I was once speaking with over this very issue: "It's refreshing to know Rome isn't the only One True Church I'm missing out on."