Before I press on the question, there are couple of things that need clearing up.
- The only reason that the silk that dominated Chinese culture comes from silkworms is that the caterpillars are herd animals whereas spiders, another silk-weaver, are loners.
- That said, spider silk poses greater interest than silkworm silk. Due to their functions as traps to capture their prey, they have to be tough. Contrary to popular belief, spider silk is stronger than steel, but not as strong as kevlar. However, it is tougher than both.
A spider silk's tensile strength is comparable to high-grade alloy steel (450-2000 MPa) and half as strong as kevlar (3000 MPa).
Spider silk has one-sixth the density of steel, but if we enlarged a single strand to the weight of a steel bar seen in 1930s news reels and 1940s cartoons, it would have been five times as strong.
Now like I said, most spiders are solitary hunters, which discourages the mass production of spider silk. But in this alternate scenario, there is a species of spider that might fit the bill--the Colonial Spider, an arachnid the size of a dime. What it lacks in size, it makes up for in numbers, behaving more like ants and termites than regular spiders. A single colony can release enough silk to smother a tree:
Now in this alternate scenario, how would the mass production of spider silk affect the way we make clothing, upholstery, window treatments, rugs, bedding, parachutes and bicycle tires?