No,
@bunyip, a railroad tie in North America refers to an 8x8" or 10x10" creosote saturated piece of wood, sometimes softwood, often hardwood, usually used, but occasionally new. Upside is that they are very termite resistant. The downside, well, creosote is a known carcinogen and contaminates land and water, not to mention that it transfers to anything that touches it.
Consumer grade new ties are often not treated to the same levels of older railroad ties. Boron treated ties are not readily obtainable for consumers. Pressure treated here tends to mean some form of copper, usually quartenary, AQS, at varying levels. The highest level is "rated for ground contact", but the fine print says that it may not be in direct contact with soil. Commercial uses tend to require excavation of the post, treatment with copper paste, wrapping to prevent water transport, and backfilling. Worth it on an electrical pole, not so much on a fence post. Treated posts can last only four or five years here in California before the subterranean termites/beetles/ants have eaten it out.
Concrete or metal sleepers exist in North America, but they aren't common. Quality concrete fence posts are basically unobtainable here. You can find cheap, but not strong or durable concrete posts. I know kiwi fruit farmers who imported concrete posts from down under after trying, but failing, to find domestic producers of comparable quality posts.
All the best,
Peter