Large banks in the U.S. and Europe are undergoing a massive and painful re-organization in order to confront the gloomy new realities of the global economic landscape.

The huge layoffs being announced at these financial institutions have occurred for as variety of factors – but, one thing unites all these companies: in the coming years, they will all be leaner, meaner and go back to their core business of lending, following four years of a brutal economic backdrop.

Friday morning, Bank of America (NYSE: BAC), the largest bank in the U.S. by assets, said it will lay off at least 3,500 people, and perhaps up to a total of 10,000, as it seeks to cut costs and streamline operations as it still labors under the burden of distressed mortgage assets on its balance sheet.

BAC’s announcement follows a flurry of similar announcements by banks across the Atlantic, including Royal Bank of Scotland (NYSE: RBS), UBS AG (NYSE: UBS), HSBC Holdings plc (NYSE: HBC), among several others.

These banking institutions plan to let go tens of thousands of people around the world, the victims of a merciless economic climate and a brutal refiguring of the global banking industry.

Peter Maris, Principal and Financial Planner at Resource Financial Group Ltd. in Wilmette, Ill., said that, generally speaking, the European/British banks are reeling from their heavy exposure to the euro zone debt crisis (particularly to Greece), while U.S. banks are trying to shake off the deleterious effects of the subprime mortgage debacle and housing collapse.

In the case of Bank of America, not only is it heavily exposed to the housing crisis (it still has billions of dollars of bad mortgage debt on its books), but it is also struggling to integrate some big acquisitions from recent years, notably Merrill Lynch and Countrywide Financial.

“Bank of America, like many other big banks are gradually going to shed the fat they acquired by getting involved in too many activities outside of their core business, which is lending,” Maris said. “They are starting to ‘un-diversify’ and streamline back to basics.”

However, in the broader context of the overall economy, Maris said he is not too concerned about the banking layoffs.

“Even though Bank of America is planning to lay off up to 10,000 workers, that’s a small portion of their 280,000-string global workforce,” he said. “Also, HSBC said they were seeking to lay off about 10 percent of its staffing over the next three years, but that process will include retirements and attrition – so it’s not really as aggressive a job cut as the media has been reporting.”

Maris explained that he would more concerned if companies like Apple (Nasdaq: APPL) of Google (Nasdaq: GOOG) started talking about job cuts.

“Apple, Google and other innovative, cutting-edge companies is where all the growth is coming from now,” Maris noted. “In contrast, the banking industry is aging and slowing down. We don’t expect to see a lot of growth there anyway.”

As bad as the current round of layoffs seems, it’s not nearly as bad as what bank employees witnessed during the credit crunch. Maris notes that the financial service industry in the U.S. underwent a 30 percent turnover in the latter half of the previous decade (that figure also includes people who voluntarily left their companies).

Looking ahead, Maris said he expects the pace of bank layoffs to persist as more banks exit from non-traditional businesses. Once that painful process is over, layoffs would likely ease in the event that banks loosen their purse-strings, start lending again and restore profit growth.