Scotland vote affects US investors: Jim O'Neill

U.S. investors should be concerned about the outcome of Scotland's vote on independence, former Goldman Sachs Asset Management Chairman Jim O'Neill said Thursday.

"Given everything you know about the last six years, people have to be worried about things going really badly wrong," he said. "So, any American investor that's got investments in what is today the U.K., if for some reason it is a 'yes,' there are certainly all sorts of complex risks to deal with."

Scottish voters are heading to the polls to decide the question of independence after 307 years of being part of the United Kingdom. Results are expected into Friday.

Read MoreScottish independence doesn't have to be a disaster

On CNBC's "Halftime Report," O'Neill said that risk premiums, for one, could be affected.

"If it is a 'yes' tomorrow, the pound will probably fall substantially, and there could be some discount applied to not just Scottish-based stocks but also British ones relative to where we are today," he said.

Beyond that, a successful Scottish call for independence could spur other nations around the world to seek self-determination, such as Spain's Basque and Catalonia regions.

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"Catalonia is a very big part of Spain," O'Neill said. "And if they do vote 'yes' in Scotland, they're going to be pushing like crazy for the same thing, and that's going to add some fresh risk premium about Spanish assets."

O'Neill also pointed to a "very weird pattern that seems to be a new trend in all sorts of places with new parties appearing out of nowhere," citing the rise of Germany's far-right AfD Party and Sweden's anti-immigrant Sweden Democrats.

"So, I think it sounds as an unpredictable style of things going on with the structure of our democracies, which we all have to try and think through, which is frankly not very easy," he said.

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O'Neill said that he didn't expect Scottish voters to choose independence.

"Well, it's obviously for nearly 5 million Scottish people to choose themselves," he said. "I personally think and have assumed even despite the wobble last week it's going to be a 'no.' I don't know whether that's my desire overtaking my judgment, but that's my assumption and I don't really see any reason to change it."

By CNBC's Bruno J. Navarro