It's hard to imagine that stockholders who own only 36 1/2 percent of the stock of Round Hill National Bank can block an attempt by First American Bankshares Inc., the principal owner, to merge it into another bank.

Nonetheless, directors of the small Virginia bank are proceeding with plans to evaluate "any merger proposal which may be received and explore possible alternatives to such a proposal."

In a letter to shareholders last week, the board declared it has a duty to determine whether a proposal to merge Round Hill National into First American Bank of Virginia would be in the best interests of the bank, its stockholders and the community. To that end, it has retained counsel to advise and represent the bank's management

Actually, Round Hill National is one of five subsidiary banks which First American Bankshares plans to merge into First American Bank in McLean. The holding company owns at least 83 percent of the stock of four other small Virginia banks and nearly 85 percent of First American of Virginia.

Although no formal merger proposal has been presented to any of the smaller banks, the holding company has instructed First American to prepare a plan for that purpose.

While the immediate impact of First American Bankshares' plan will be felt at its subsidiary banks, the long-term effect is something that competitor holding companies and major banks in the region must be contemplating.

And the prospect of an expansion move by First American Bankshares is as much a dilemma for competitors as it is for the 100 or so Round Hill National stockholders who will be offered a chance to exchange their shares for First American Bank stock.

By itself, a consolidation of First American Bankshares' holdings in Virginia would have little impact on banking in the state. But a different set of considerations come into play when you include the company's plan to merge First Peninsula Bank & Trust Co. of Hampton into First American Bank and its purchase of 26 branches from two other Virginia holding companies.

Even if First American Bankshares completes all of those transactions, First American Bank's assets would be about $2 billion. That is considerably smaller than the state's biggest banking institution and pales by comparison with the bank that a pending merger between First & Merchants Corp. and Viriginia National Bankshares would produce.

But an expansion would give First American parity in terms of access to other markets in the state. The mergers and acquisitions would extend its coverage from Northern Virginia to Tidewater to the far southwestern part of the state.

Of more importance to regional banking interests, however, is the likelihood that First American Bankshares' Virginia strategy of consolidation and merger will be repeated in Maryland, where it has a majority interest in First American Bank of Maryland and the smaller Eastern Shore National Bank in Pocomoke City.

With a majority interest also in First American Bank of Washington, First American Bankshares holds a strategic advantage over other bank holding companies in the region. It is the only bank holding company with banks in the District, Maryland and Virginia and has given every indication that it will seek to strengthen its position in the market.

"This bank holding institution is unique, possessing as it does a multi-state charter unavailable to any other commercial banking operation in the eastern half of our country," First American Bankshares' Chairman Clark M. Clifford stated last year.

Indeed, if local banks do succeed in winning approval for limited interstate banking in the region, First American Bankshares is in a commanding position to take advantage of it before competitors can act.

If it wasn't clear early on why a group of Middle Eastern investors would spend more than $200 million in a four-year struggle for control of First American Bankshares (formerly Financial General Bankshares Inc.), it should be by now.

Not only did the company's previous management fail to take advantage of banking opportunities in this region, it failed to recognize what the new owners discerned five years ago when they made their move to acquire control of Financial General. As one of a handful of multi-bank holding companies with banks in four states and the District, it offers unlimited potential for developing major commercial banking operations.