SEATTLE in late summer can be unforgettable - with spectacular scenic views. That's how the city was last week. It was a time for two important meetings there, the annual summer gathering of the National Governors' Association and the trilateral meeting of trade representatives from the United States, Canada, and Mexico working to produce a North American free-trade pact.It was only fitting that the governors and the trade delegates should be in the same community last week. The governors and trade ministers were both addressing similar concerns: how to find the vision for the growth needed to meet pressing social challenges following an economic downturn. The governors urged major reform of the expensive US health care system - a system now straining the resources of many states. Meantime, US Trade Representative Carla Hills and her counterparts from Canada and Mexico were telling the governors that a free-trade agreement would foster growth. Many states have benefited from growing continental trade. Between 1987 and 1989, 45 states and the District of Columbia boosted exports to Mexico. Expanding exports, whether within the Western Hemisphere or elsewhere, is not by itself a panacea for state budget woes. But it is part of a solution. As US states grow economically, they create new wealth and enrich their tax coffers. The US and Canada have now entered into a free-trade agreement. Extending the concept to embrace Mexico makes good sense. Unfortunately, the White House is leaving a broad roster of social concerns outside the main trade pact - such as pollution standards, worker safety measures, and wage disparities. Such issues are to be considered in a separate program between the respective governments. But all these social concerns should be addressed within the broad trade agreement. Negotiators must ensure that a trilateral trade pact sets the highest possible standards. Ensuring such standards would benefit all North Americans - and, in the process, enable financially hard-pressed state governors to tell their constituencies that they can enthusiastically support a growth-oriented trilateral free trade agreement.