We can see a shrinking navy coming. Our nuclear submarines are just too expensive, as Strategypage writes:
The U.S. Navy continues to debate the issue of just how effective non-nuclear submarines would be in wartime and whether the U.S. should buy some of these non-nuclear boats itself. This radical proposal is based on two compelling factors. First, the U.S. Navy may not get enough money to maintain a force of 40-50 SSNs (attack subs). Second, the quietness of modern diesel-electric boats puts nuclear subs at a serious disadvantage, especially in coastal waters. With modern passive sensors, a submerged diesel-electric sub is often the best weapon for finding and destroying other diesel-electric boats. While the nuclear sub is the most effective high seas vessel, especially if you have worldwide responsibilities and these nukes would have to quickly move long distances to get to the troubled waters, the diesel electric boat, operating on batteries in coastal waters, is quieter and harder to find.
Yes, we need bigger boats (and ships) because our vessels must travel across oceans to reach patrol areas rather than sailing out of port to fight close by as many nations can plan to do. But we did have diesel-electrics in World War II, obviously, and they operated in the western Pacific effectively.
Our conventionally powered subs would need to be bigger boats--as Australia must have--rather than the small boats that the Germans, for example, could build for their primary theaters of the Baltic and North Sea.
If we build diesel-electrics, we could team with Australia and perhaps Canada, who also need longer-legged boats, for design and volume construction.
We could also provide an option for Taiwan to acquire boats by regaining our conventional submarines construction capabilities.
While we couldn't replace all our nuclear submarines with conventional boats, the portion of our sub fleet forward deployed in the western Pacific could be mostly diesel-electrics. Based in Japan or operating out of the Philippines, Guam, Singapore, or Australia, these conventional boats would have much shorter deployment cruises than our nuclear-powered boats based in the continental United States or Hawaii.
If we really need a minimum number of hulls to carry out our needed missions, act like we need a minimum number of hulls. The money isn't there to build the types of ships and boats the Navy is building. If the Navy keeps building those ships and boats in the hope that somehow the money will appear, the Navy won't get the numbers it wants. That's a choice, too.