So, being a little pedantic, the answer to your question is "no". I say that because you asked "generally speaking...". I answer "no" because there is no general cultural rule to draw from to answer your question. Some companies are perfectly fine with this, others are not. This is much like saying, "what's the dress code?" or "what's the software language a company uses" without knowing what company you're talking about.
I have seen many companies that are OK with napping, many others which are not. Some even set up nap rooms to encourage the behavior, others do not. Some allow it by policy, but then the peer culture is such that you're not tolerated by your coworkers if you take advantage of that corporate leniency.
Sometimes it's really counter to what you might expect from other cultural norms. I've seen companies that have a strict dress code and hours of business that are more lax on sleeping at your desk than others which let folks come and go as they please and wear whatever they want.